(maint) Remove duplication from selinux facts

Prior to this commit, the selinux fact had code duplication. This commit
abstracts this duplication to a hash of fact name and label.
(maint) Remove duplication from virtual fact

Prior to this commit the SunOS and OpenBSD resolutions for the virtual
fact had duplicate logic. This commit abstracts the logic into the
`Facter::Util::Virtual.parse_virtualization` helper.
Merge pull request #443 from briancain/maint/master/remove_dup_from_selinux

(maint) Remove duplication from selinux facts
Merge pull request #444 from ajroetker/maint/master/remove_duplication_from_virtual_fact

(maint) Remove duplication from virtual fact