Use addClassResourceCleanup to cleanup floatingips
Use addClassResourceCleanup to cleanup floatingips

This is to use addClassResourceCleanup for the cleanup of floatingips,
so the cleanup in resource_cleanup can be removed.

Change-Id: If8fdf2278b1b70f94816c4fe1a78566c8ac999a5

masayukig/tempest,masayukig/tempest,cisco-openstack/tempest,openstack/tempest,openstack/tempest,cisco-openstack/tempest