fix associating a floating IP during floating IP creation.
fix associating a floating IP during floating IP creation.

bug 1038962

also add check to make sure that floating IP's are only associated if
the upstream router has a external network gateway to the appropriate
external network.

Change-Id: Ie4cb632296ce4a1cb989242eb894d73a7488cdb3

gkotton/vmware-nsx,gkotton/vmware-nsx