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