command_process_create_cell: calls channel_send_destroy() for already exist circuit
command_process_create_cell tries to check several conditions and can to call
channel_send_destroy for already exist circuit.
channel_send_destroy is more complex mechanism than sending of some cell as it happened before.
It shouldn't to call
circ_id already exist for
chan. It should to check
circ_id and drop if already exist and only then to check all another stuff.