(#18756) Fix getting interface specific data with newer net_tools

A simple regexp, and then some spec tests to verify that it works with
1.60 version, as well as 2.0 version of ifconfig output.
Update the fixtures to include a "real" ipv6 address

Also, update the 1.60 fixture to use the older format, so that this test
actually verifies both outputs of ifconfig $iface
Add ipaddress6_$iface fact checks to verify the "real" ipv6 addresses

It automatically ignores ones link-local, so I faked it :)
Merge branch 'dkowis-18756_ip_regex'

* dkowis-18756_ip_regex:
  Add ipaddress6_$iface fact checks to verify the "real" ipv6 addresses
  Update the fixtures to include a "real" ipv6 address
  (#18756) Fix getting interface specific data with newer net_tools

closes #390