ceph-disk: trigger must ensure device ownership

ceph-disk: trigger must ensure device ownership

The udev rules that set the owner/group of the OSD devices are racing
with 50-udev-default.rules and depending on which udev event fires last,
ownership may not be as expected.

Since ceph-disk trigger --sync runs as root, always happens after
dm/lvm/filesystem units are complete and before activation, it is a good
time to set the ownership of the device.

It does not eliminate all races: a script running after systemd
local-fs.target and firing a udev event may create a situation where the
permissions of the device are temporarily reverted while the activation
is running.

Fixes: http://tracker.ceph.com/issues/17813
Signed-off-by: Loic Dachary <loic@dachary.org>