rgw: fix radosgw start-up script.

radosgw init script is unable to start radosgw daemon.
as it is relies on requiretty being disabled.
once init script start this daemon with sudo it fails
to start the daemon.

changing 'sudo' to 'su', it will fix this issue and
will also help running radosgw daemon with our new
"ceph" UID project.

Fixes: ceph#10927

Signed-off-by: Vikhyat Umrao <vumrao@redhat.com>
(cherry picked from commit c835422)

src/init-radosgw

@@ -102,7 +102,7 @@ case "$1" in
 	    if [ $DEBIAN -eq 1 ]; then
 		start-stop-daemon --start -u $user -x $RADOSGW -- -n $name
 	    elif [ -n "$SYSTEMD_RUN" ]; then
-                $SYSTEMD_RUN -r sudo -u "$user" bash -c "ulimit -n 32768; $RADOSGW -n $name"
+                $SYSTEMD_RUN -r su "$user" -c "ulimit -n 32768; $RADOSGW -n $name"
             else
 		ulimit -n 32768
                 daemon --user="$user" "$RADOSGW -n $name"