(#12116) Don't break on the first interface

Previously, if there were multiple interfaces with IPEnabled on Windows,
we would always use the DNSDomain value from the first interface, even
if it was nil or empty.

This commit changes the domain fact to look for the first non-nil and
non-empty DNSDomain value.
Merge pull request #520 from joshcooper/ticket/stable/12116_first_non_nil_dnsdomain

(#12116) Don't break on the first interface
(packaging) Update FACTERVERSION to 1.7.3-rc1