ensure summary is looked for the user we need (part 2)

ensure summary is looked for the user we need (part 2)

Move the get_user_summary(out, user) logic to util.rgw so that it can be
shared between radosgw_admin_rest.py and radosgw_admin.py and modify
them accordingly.

http://tracker.ceph.com/issues/11180 Fixes: #11180

Signed-off-by: Loic Dachary <loic@dachary.org>
(cherry picked from commit 97e6d808f086834f2350084d5de36be285ad2bde)

Conflicts:
	tasks/radosgw_admin.py
        the context around def successful_ops(out): changed but is
	unrelated to the modification