rgw: default auth_client_required=cephx

rgw: default auth_client_required=cephx

This makes this warning go away:

2021-08-09T15:51:52.882+0000 7f2373837400 -1 warn_if_insecure(): WARNING: rgw is configured to optionally allow insecure connections to the monitors (auth_supported, ms_mon_client_mode), ssl certificates stored at the monitor configuration could leak

7e22d2a31d277ab3eecff47b0864b206a32e2332 only fixed half of the problem.

Signed-off-by: Sage Weil <sage@newdream.net>
(cherry picked from commit 6010eae66cd12358880fff64e2229a4265a5cf0a)