init-radosgw: do not use systemd-run in sysvinit

init-radosgw: do not use systemd-run in sysvinit

`systemd-run` logic in initscripts was introduced because of ticket
http://tracker.ceph.com/issues/7627.

If we have systemd-based operating system, we should use systemd unit files
from systemd directory to start/stop ceph daemons.
Otherwise, `daemon()` from `/etc/init.d/functions` on systemd distro starts service
in `system.slice` and everything works well.

`systemd-run` can not be run on non-systemd distros, so it's not needed
on SysV systems.

also, ceph-disk is now able to run the "systemctl"
to enable and start the ceph-osd, and ceph-deploy is also now
playing well with systemd when it comes to ceph-mon and ceph-mds

Fixes: http://tracker.ceph.com/issues/16440
Signed-off-by: Vladislav Odintsov <odivlad@gmail.com>
(cherry picked from commit 1fd4f92a025e80092b8d08d9b7da2e0b73a52f0f)