fix(account): Provide defaults to avoid NPEs

An account without requiredGroupMembership or permissions is a
valid account. However, certain areas of the code assume that these
values are not null and therefore encounter NullPointerExceptions.
To avoid this, initialize these fields to a reasonable default value.

clouddriver-aws/src/main/java/com/netflix/spinnaker/clouddriver/aws/security/config/AccountsConfiguration.java

@@ -57,8 +57,8 @@ public static class Account implements AccessControlledAccountDefinition {
     @Include private Boolean enabled;
     @Include private List<CredentialsConfig.Region> regions;
     @Include private List<String> defaultSecurityGroups;
-    private List<String> requiredGroupMembership;
-    @Include private Permissions.Builder permissions;
+    private List<String> requiredGroupMembership = new ArrayList<>();
+    @Include private Permissions.Builder permissions = new Permissions.Builder();
     @Include private String edda;
     @Include private Boolean eddaEnabled;
     @Include private Boolean lambdaEnabled;