rgw: only log metadata on metadata master zone

Fixes: http://tracker.ceph.com/issues/20244

Signed-off-by: Casey Bodley <cbodley@redhat.com>
(cherry picked from commit b8272f3)

src/rgw/rgw_rados.h

@@ -3175,7 +3175,7 @@ class RGWRados
   }
 
   bool need_to_log_metadata() {
-    return get_zone().log_meta;
+    return is_meta_master() && get_zone().log_meta;
   }
 
   librados::Rados* get_rados_handle();