Merge pull request #8880 from cbodley/wip-rgw-zonegroup-remove

radosgw-admin: add missing 'zonegroup remove'

Reviewed-by: Yehuda Sadeh <yehudasa@gmail.com>

diff --cc src/rgw/rgw_admin.cc
Simple merge

diff --cc src/rgw/rgw_rados.cc
Simple merge

diff --cc src/test/rgw/test_multi.py
Simple merge