HotMigrationJob now use asynchronous calls for drbd connect

        # start connection of drbd:

        self.report(status_msg % 'connect')

        source.proxy.drbd_connect(res_src, res_dst, dest.ip)

        dest.proxy.drbd_connect(res_dst, res_src, source.ip)

        watcher = AsyncWatcher()

        watcher.register(source.conn, 'drbd_connect', res_src, res_dst, dest.ip)

        watcher.register(dest.conn, 'drbd_connect', res_dst, res_src, source.ip)

        msgs = watcher.wait(timeout=30)

        for msg in msgs:

            if 'error' in msg:

                msg = 'error while drbd_connect: %s' % msg['error']['message']

                raise JobCancelError(msg)

        # setup topology as primary/secondary:

        source.proxy.drbd_role(res_src, True)