BYE is not sent when 200/OK is not ACK-ed

[riza]

Scenario:

1. Make call from device A to device B
2. Answer the call on device B and disconnect immediately.
3. In case device B disconnected the call (hangup) and ACK is lost, BYE will not be send and call will not be disconnected.

In case device B didn't hangup, timeout will occur and BYE is sent
(200/OK is not ACK-ed).

BYE will be delayed until ACK is received or the dialog is confirmed (see #1712). On a non confirmed dialog, BYE is only allowed to be sent when there's a timeout or transport error.
On the above case, B's manual hangup will have cause 603, hence BYE is delayed (until ACK is received or tsx timeout or transport error) . However when the timeout occur, The BYE won't be sent and still got delayed because the cause can not be set due to this check on inv_set_cause:

(cause_code > inv->cause)

Thanks to Nir Lavi for the report.

[riza]

In 5104:

Re #1857: (Fix) BYE is not sent when 200/OK is not ACK-ed