Fixed the issues on deleting resources

If lb port was not connected, destroyResouces() was failing on destroying resources,
Fixed it by making them conditional.

neutron port-list is slower than nova floatingip-list,
so changed the logic to use nova floatingip-list to get floating IP,
then get fip_id using neutron floatingIP and delete them.

Also removed calling _fail if keypair-delete fail which was causing a loop.