Reset HOLD/SWAP state after SRVCC

If there was a hold/swap in progress during SRVCC, the state
was not being cleared correctly, causing it to remain in that state
when the next call began.

Bug: 161076702
Test: atest FrameworksTelephonyTests:ImsPhoneCallTrackerTest
Change-Id: Ic84bd04a0084a55e4b6071a353548d658a925d2b