Installs the tgt gateway

Currently relies on the client.admin key being installed on the system
Fixes the tgt service on Ubuntu

The ceph version of tgt does not provide an Upstart service
Fixes the case where no mon IPs can be found

When searching through mons for an IP in the public subnet, if no routes
match the public network, it returns the mon's entire network object
which then gets outputted to the ceph.conf file and generally breaks things.
This prevents that occurrence.
Merge remote-tracking branch 'hufman/fix-empty-mons' into 89
Merge remote-tracking branch 'hufman/feature-tgt' into 88