Fix bad searching of reverse DNS zone
There was a problem with finding correct DNS zone. It found a first substring match.
Therefore when there was location 0.10.10.in-addr.arpa. and 110.10.10.in-addr.arpa
the location for IP address 10.10.110.1 was the first one, which is incorrect. Now
it finds the second one, because it finds the longest match.
https://fedorahosted.org/freeipa/ticket/5796
Reviewed-By: Petr Vobornik <pvoborni@redhat.com>