Changed participant status for the connecting external call.
This prevents the situation where during a call transfer, if an Agent presses the Hang Up button before the external transferred call is answered, the conference is ended for all parties.
Agent1 receives call from customer1
Agent1 makes external call to customer2
Agent1 press 'Leave Call' while the call is ringing, the call will continue ringing and connect between customer1 and customer2
Changed participant status for the connecting external call.
This prevents the situation where during a call transfer, if an Agent presses the Hang Up button before the external transferred call is answered, the conference is ended for all parties.