Somewhat revert I7087701c63906f2a9843a4479947eb4fe8c7fd4e

The tempest_default_ip doesn't need to be a new fact. This was already
in the iptables defaults, but commented out. Uncommented the default,
and changed the task to match the tempest_ip name.

Change-Id: Ic69057b25f9cd378b536c40ee71295f5ed223d87