Consistently use goEnumPrefix and fix bug generating enum default val…

…ue in wrapper union node. (#511)

Consistently use goEnumPrefix and fix bug generating enum default value in wrapper union node.

### Background
The recent union default value generation changes [removed a call to `enumDefaultValue`](https://github.com/openconfig/ygot/pull/496/files#diff-19ecb3e61250b63aaf93a11d7017203a90637b52bee811a021ab253b01c42748L275-L277) in order to use the *raw* default value string provided in the YANG file to look up the existence of the enum value in goyang's AST before accepting the default value as an enum type. The `yangDefaultValueToGo` function only processes these raw values for simplicity. However, this breaks generating typedef enums in wrapper union mode because a call to `enumDefaultValue` is required to make the output correct.

### This change
What this change does is that during the processing of both inline and typedef enumerated values by `yangTypeToGoType`, `enumDefaultValue` is **not called** when populating `MappedType`'s `DefaultValue` field. This means that **all** enumerated values that subsequently get processed by `yangDefaultValueToGo`, which come after the call to `yangTypeToGoType`, will see the raw default value. Most importantly, `goLeafDefault`, a call that happens in wrapper-union mode, can now transform the raw default values for enums into their "cooked" versions without discriminating between inline and typedef enumerated values. This is what fixes this problem.

exampleoc/ocpath.go

@@ -3,7 +3,7 @@ Package exampleoc is a generated package which contains definitions
 of structs which generate gNMI paths for a YANG schema. The generated paths are
 based on a compressed form of the schema.
 
-This package was generated by /Users/robjs/Code/go/src/github.com/openconfig/ygot/genutil/names.go
+This package was generated by /usr/local/google/home/wenbli/gocode/src/github.com/openconfig/ygot/genutil/names.go
 using the following YANG input files:
 	- public/release/models/network-instance/openconfig-network-instance.yang
 	- public/release/models/optical-transport/openconfig-optical-amplifier.yang
@@ -36526,6 +36526,28 @@ func (n *ComponentPathAny) SerialNo() *Component_SerialNoPathAny {
 	}
 }
 
+// SoftwareModule returns from ComponentPath the path struct for its child "software-module".
+func (n *ComponentPath) SoftwareModule() *Component_SoftwareModulePath {
+	return &Component_SoftwareModulePath{
+		NodePath: ygot.NewNodePath(
+			[]string{"software-module"},
+			map[string]interface{}{},
+			n,
+		),
+	}
+}
+
+// SoftwareModule returns from ComponentPathAny the path struct for its child "software-module".
+func (n *ComponentPathAny) SoftwareModule() *Component_SoftwareModulePathAny {
+	return &Component_SoftwareModulePathAny{
+		NodePath: ygot.NewNodePath(
+			[]string{"software-module"},
+			map[string]interface{}{},
+			n,
+		),
+	}
+}
+
 // SoftwareVersion returns from ComponentPath the path struct for its child "software-version".
 func (n *ComponentPath) SoftwareVersion() *Component_SoftwareVersionPath {
 	return &Component_SoftwareVersionPath{
@@ -39662,6 +39684,16 @@ func (n *Component_PropertyPathAny) Value() *Component_Property_ValuePathAny {
 	}
 }
 
+// Component_SoftwareModulePath represents the /openconfig-platform/components/component/software-module YANG schema element.
+type Component_SoftwareModulePath struct {
+	*ygot.NodePath
+}
+
+// Component_SoftwareModulePathAny represents the wildcard version of the /openconfig-platform/components/component/software-module YANG schema element.
+type Component_SoftwareModulePathAny struct {
+	*ygot.NodePath
+}
+
 // Component_StoragePath represents the /openconfig-platform/components/component/storage YANG schema element.
 type Component_StoragePath struct {
 	*ygot.NodePath
@@ -68728,6 +68760,16 @@ type NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_LsrIdPathAny struct {
 	*ygot.NodePath
 }
 
+// NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePath represents the /openconfig-network-instance/network-instances/network-instance/mpls/signaling-protocols/ldp/neighbors/neighbor/state/session-state YANG schema element.
+type NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePath struct {
+	*ygot.NodePath
+}
+
+// NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePathAny represents the wildcard version of the /openconfig-network-instance/network-instances/network-instance/mpls/signaling-protocols/ldp/neighbors/neighbor/state/session-state YANG schema element.
+type NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePathAny struct {
+	*ygot.NodePath
+}
+
 // Authentication returns from NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPath the path struct for its child "authentication".
 func (n *NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPath) Authentication() *NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_AuthenticationPath {
 	return &NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_AuthenticationPath{
@@ -68890,6 +68932,28 @@ func (n *NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPathAny) LsrId() *N
 	}
 }
 
+// SessionState returns from NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPath the path struct for its child "session-state".
+func (n *NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPath) SessionState() *NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePath {
+	return &NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePath{
+		NodePath: ygot.NewNodePath(
+			[]string{"state", "session-state"},
+			map[string]interface{}{},
+			n,
+		),
+	}
+}
+
+// SessionState returns from NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPathAny the path struct for its child "session-state".
+func (n *NetworkInstance_Mpls_SignalingProtocols_Ldp_NeighborPathAny) SessionState() *NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePathAny {
+	return &NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_SessionStatePathAny{
+		NodePath: ygot.NewNodePath(
+			[]string{"state", "session-state"},
+			map[string]interface{}{},
+			n,
+		),
+	}
+}
+
 // NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_AuthenticationPath represents the /openconfig-network-instance/network-instances/network-instance/mpls/signaling-protocols/ldp/neighbors/neighbor/authentication YANG schema element.
 type NetworkInstance_Mpls_SignalingProtocols_Ldp_Neighbor_AuthenticationPath struct {
 	*ygot.NodePath