upstart: radosgw-all does not start on boot if ceph-base is not installed
The "radosgw-all" Upstart service depends on the "ceph-all" service in order to trigger a start operation.
ceph-all.conf ships in the "ceph-base" package (in Jewel and newer) or the "ceph" package (Hammer and older), and this is not an explicit radosgw package dependency. This means that the radosgw-all Upstart service would not start on boot unless the ceph-base package was also explicitly installed.
We can break this dependency by starting radosgw-all according to the system's runlevel, rather than only listening for the ceph-all starting signal.
(From what I can tell from Git, this has been an issue on Ubuntu since the introduction of Upstart support)