Fix for floatingip-delete not removing fip_gw port

fip_agent_gateway_port is created dynamically on a
compute node where FIP namespace is created. When
floatingip-disassociate is called this 'port' is
deleted.

But when we call floatingip-delete this port is
not deleted.

This patch fixes the issue mentioned above.

Closes-Bug: #1351066

Change-Id: I1aa51680394547390546fe362abfae7a5d25425b
Merge "Fix for floatingip-delete not removing fip_gw port"