rgw: fix radosgw start-up script.

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 upstream: #10927
Fixes downstream: #1238521

Reviewed-by: Ken Dreyer <kdreyer@redhat.com>
Signed-off-by: Vikhyat Umrao <vumrao@redhat.com>
(cherry picked from commit c83542296aeb8f5dd96f5d9e09327e7a89370742)