Updates a floatingip, disassociates the floating ip if
        port is set to `None`

def update_floatingip(self, floatingip_id, port=None):
        '''
        Updates a floatingip, disassociates the floating ip if
        port is set to `None`
        '''
        if port is None:
            body = {'floatingip': {}}
        else:
            port_id = self._find_port_id(port)
            body = {'floatingip': {'port_id': port_id}}
        return self.network_conn.update_floatingip(
            floatingip=floatingip_id, body=body)