ip address fact that return full ifconfig output

On system with non english locale, the ip address fact return full ifconfig
output.
(refactor) Simplify ipaddress fact specs
(maint) Stub extraneous facts when testing ifconfig

If the higher weight ifconfig fact fails to resolve, Facter will try to
determine the IP address by resolving the hostname. When testing to
ensure that the ifconfig based resolution returns nil, the resolution
fact will be called and return an unexpected value. This commit stubs
the hostname fact when testing the ifconfig ipaddress resolution to
ensure the tests behave consistently.
Merge branch 'pull-476' into stable

This closes GH-476