HFP Client call status update

When a call is terminating only inform telecom about its termination
when there is an actual state change from the attached phone.

Bug: 138753272
Test: start and end call, observe logs from HfpClientDeviceBlock that a
closing call still in its previous state doesn't get destroyed
prematurely.

Change-Id: Ia5d105daa239f64b73c058d064c2e5181d862e4e