Deletes a port on OVS instance.

        This method is corresponding to the following ovs-vsctl command::

            $ ovs-vsctl del-port <bridge> <port>

def del_port(self, port_name):
        """
        Deletes a port on OVS instance.

        This method is corresponding to the following ovs-vsctl command::

            $ ovs-vsctl del-port <bridge> <port>
        """
        command = ovs_vsctl.VSCtlCommand('del-port', (self.br_name, port_name))
        self.run_command([command])