MXS-1712 Add reset replication to MariaDB Monitor

The 'reset_replication' module command deletes all slave connections and binlogs,
sets gtid to sequence 0 and restarts replication from the given master. Should be
only used if gtid:s are incompatible but the actual data is known to be in sync.

server/modules/monitor/mariadbmon/mariadbserver.hh

@@ -489,6 +489,14 @@ public:
      */
     bool disable_events(BinlogMode binlog_mode, json_t** error_out);
 
+    /**
+     * Stop and delete all slave connections.
+     *
+     * @param error_out Error output
+     * @return True if successful. If false, some connections may have been successfully deleted.
+     */
+    bool reset_all_slave_conns(json_t** error_out);
+
 private:
     class EventInfo;
     typedef std::function<void (const EventInfo&, json_t** error_out)> ManipulatorFunc;