obs-utils: ship obs_mirror_project.

Reviewed-by: Sjoerd Simons &lt;Sjoerd Simons <sjoerd.simons@collabora.co.uk&gt;>
Differential Revision: https://phabricator.collabora.co.uk/D1122

debian/obs-utils.install

-# dist/obs_mirror_project         /usr/sbin/
-# dropped on 2.5
-# install obs mirror script and obs copy script
+# install obs mirror script and project update script
+dist/obs_mirror_project		/usr/sbin
 usr/sbin/obs_project_update