Configure /etc/resolv.conf when in DC mode

- This should probably also set an AD DC as the nameserver when AD is
  configured

Conflicts:
	gui/common/freenasldap.py
	nanobsd/Files/etc/directoryservice/DomainController/ctl
	nas_ports/freenas/freenas-files/Makefile
	nas_ports/freenas/freenas-files/pkg-plist