waitUntilUp also wait for IPv6 if statically configured

Need to add `ndisc6` to the install.img

Signed-off-by: BenjiReis <benjamin.reis@vates.fr>

netinterface.py

@@ -214,13 +214,17 @@ def writeRHStyleInterface(self, iface):
 
 
     def waitUntilUp(self, iface):
-        if not self.isStatic4():
-            return True
-        if not self.gateway:
-            return True
+        iface_name = self.getInterfaceName(iface)
+        if self.isStatic4() and self.gateway:
+            rc = util.runCmd2(['/usr/sbin/arping', '-f', '-w', '120', '-I',
+                           iface_name, self.gateway])
+        if rc != 0:
+            return False
+
+        if self.isStatic6() and self.ipv6_gateway:
+            rc = util.runCmd2(['/usr/sbin/ndisc6', '-1', '-w', '120',
+                               self.ipv6_gateway, iface_name])
 
-        rc = util.runCmd2(['/usr/sbin/arping', '-f', '-w', '120', '-I',
-                           self.getInterfaceName(iface), self.gateway])
         return rc == 0
 
     @staticmethod