Permanently switches the current connection to the new data center.

async def _switch_dc(self, new_dc):
        """
        Permanently switches the current connection to the new data center.
        """
        self._log[__name__].info('Reconnecting to new data center %s', new_dc)
        dc = await self._get_dc(new_dc)

        self.session.set_dc(dc.id, dc.ip_address, dc.port)
        # auth_key's are associated with a server, which has now changed
        # so it's not valid anymore. Set to None to force recreating it.
        self._sender.auth_key.key = None
        self.session.auth_key = None
        self.session.save()
        await self._disconnect()
        return await self.connect()