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
Merge "Prevent external router IPs from being sent back"