fine-grained control systemd to start/stop/restart ceph services at once
Currently ceph has only one systemd unit file - ceph.target to start/stop all the ceph services at once on one machine. If we deploy multiple services on one machine, like osd, mon and mds, we can't start/stop each of them separately at once.
So having more fine-grained control to each kind of service by adding target file to each of them. This will make convenient to only start/stop osd instances at once especially.