Fix call scenario when the CALL_REJECT is received for internal call

When the internal call "0000" is proceeded from any of DECT handset, busy tone is heared since we always use
extension_id=0 for the first outgoing call and the call is directed to the same extension_id = 0. In this
case CALL_REJECT is received by asterisk, but connection is not closed due to another channel_state value.
Fix it so that connection is properly closed in this case.