Removes the --user flag from the systemd based mount command in the
Quobyte driver. This prevents mount failures due to:
- Older systemd releases not supporting the --user flag (e.g. CentOS)
- Systemd versions having a bug preventing running the --scope and
--user flags together
- processutils context not allowing mount to run with this flag
(see bug referenced below for details)
Furthermore the systemd detection is fixed and
all mount and umount commands are moved to libvirt privsep.
Closes-Bug: #1756823
Change-Id: I53f3a062ce419d1142d7dd3103fab565bb105e05
7231f7dee1