MXS-1712 Cleanup reset-replication

Now logs messages explaining what has been done. Scheduled events are
disabled/enabled during the operation. Redirection of slaves is done at
the end similar to failover/switchover.

server/modules/monitor/mariadbmon/mariadbserver.cc

@@ -1311,6 +1311,11 @@ bool MariaDBServer::reset_all_slave_conns(json_t** error_out)
             break;
         }
     }
+
+    if (!error && !m_slave_status.empty())
+    {
+        MXS_NOTICE("Removed %lu slave connection(s) from '%s'.", m_slave_status.size(), name());
+    }
     return !error;
 }