Gather facts on localhost before running them to learn the IP
address of the network_interface, which, in turn, is needed
for the default value of ironic_url.
Do not try to fetch interface information from target hosts,
best case it will fail, worst case - will provide IP information
from hosts themselves.
Change-Id: Ib884c739457fa6e4d0159441c2ae855af61c55c1