Fix up Network dns_search resolve.conf support

Prior problems:

* Was using a bogus resolver.conf name instead of resolv.conf
* Didn't have persistent change support for RHEL
* Would replace /etc/resolv.conf symlink on Ubuntu, causing problems

Also renamed prop to dns_search (allowing list) and dns_domain alias
Bump to version 2.1.2
Merge branch 'network-dns-search' into 2.1.x
History for merge, 2.1.2 release