bz#1152516 don't autostart networking in discovery image

per https://groups.google.com/forum/#!topic/foreman-dev/wg0ETtQBH9k

Signed-off-by: Mike Burns <mburns@redhat.com>
Merge pull request #104 from mburns72h/discovery-no-net

bz#1152516 don't autostart networking in discovery image