When an NFS check restarts a failed service by hand then systemd will
be unable to stop or start this service again because (at least) the
PID file will be wrong.  Do this via the NFS Linux kernel call-out
instead.  Allow the call-out to use the services instead of doing
manual restarts.  Add variables for mount, status and rquotad services
to support this.

Adding systemd NFS services to the call-out will follow.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13860



Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@samba.org>
(cherry picked from commit 42103b56)