floatingip bind a vm, it can not be deleted and return a error status
code to openstack, but openstack do not deal with the error status code
and delete the floatingip, and this lead to APEX'functiontest does not
pass, so we have modified the code logic and allowed to delete the
floatingip which have bind a vm.
Change-Id: I0355fd53ba6235c17ec868b9b48ba906b4d07784
163ea83ca2