Reset hold states on exception

When swap is pressed first hold command is sent on active call
and then resume command is sent on held call.But since conference
will be in process both the commands will not be processed and
exception will be thrown to ImsPhoneCallTracker holdActiveCall
funtion from ImsCall hold function.
When the exception is received holdActiveCall is not resetting
the mHoldSwitchingState resulting in the issue.
Also when unholdCall receives exception mHoldSwitchingState is
not reset and foregroundcall and background call are not switched back.

Reset the ​mHoldSwitchingState on exception and switch back the calls.

Change-Id: I88b166c6b4a4bd077ad99602c9fa44534ce99ee7
CRs-Fixed: 2521283