rgw: default ms_mon_client_mode = secure

Require a secure connection to the monitor.  This is important because
we may store SSL certs on the mon.

Note that secure mode was introduce before Nautilus, so this can be
backported at least to Pacific.

Fixes: https://tracker.ceph.com/issues/52000
Signed-off-by: Sage Weil <sage@newdream.net>

src/rgw/rgw_main.cc

@@ -190,7 +190,8 @@ int radosgw_Main(int argc, const char **argv)
   map<string,string> defaults = {
     { "debug_rgw", "1/5" },
     { "keyring", "$rgw_data/keyring" },
-    { "objecter_inflight_ops", "24576" }
+    { "objecter_inflight_ops", "24576" },
+    { "ms_mon_client_mode", "secure" }
   };
 
   vector<const char*> args;