dns: Remove the resolv.conf 6 entry limit

The resolv.conf used to have a limit of 6 entries for the search option. With later versions of glibc, this limit has been removed. As a result, remove the limit here so that all search entries set will be applied to the resolv.conf. If there is a limit imposed by older versions of glibc, it should be imposed there as opposed to within NetworkManager.

Fixes #80 (closed)