Prevent external router IPs from being sent back

In anticipation of change Iba7c606eea48181fc10e9d0d5dc667e6f48f37de
being merged or at least a minimum a fix for bug #1255142, the
router response will have external IP address information available
that is not mutable by a regular tenant. This patch removes that
information from the response before replaying it back for a router
update.

Change-Id: Id1da9246bca2a2eee69f751856ffa7052eb18ef9
diff --git a/tempest/services/network/json/network_client.py b/tempest/services/network/json/network_client.py
index 78ed56f..46475f0 100644
--- a/tempest/services/network/json/network_client.py
+++ b/tempest/services/network/json/network_client.py
@@ -85,8 +85,14 @@
         update_body['admin_state_up'] = kwargs.get(
             'admin_state_up', body['router']['admin_state_up'])
         cur_gw_info = body['router']['external_gateway_info']
-        if cur_gw_info and not set_enable_snat:
-            cur_gw_info.pop('enable_snat', None)
+        if cur_gw_info:
+            # TODO(kevinbenton): setting the external gateway info is not
+            # allowed for a regular tenant. If the ability to update is also
+            # merged, a test case for this will need to be added similar to
+            # the SNAT case.
+            cur_gw_info.pop('external_fixed_ips', None)
+            if not set_enable_snat:
+                cur_gw_info.pop('enable_snat', None)
         update_body['external_gateway_info'] = kwargs.get(
             'external_gateway_info', body['router']['external_gateway_info'])
         update_body = dict(router=update_body)