Address #4573 Check interface keys and return gracefully on solaris zones

system/setup

@@ -1732,6 +1732,8 @@ class GenericBsdIfconfigNetwork(Network):
     def merge_default_interface(self, defaults, interfaces, ip_type):
         if not 'interface' in defaults.keys():
             return
+        if not defaults['interface'] in interfaces:
+            return
         ifinfo = interfaces[defaults['interface']]
         # copy all the interface values across except addresses
         for item in ifinfo.keys():