HeadsetService: Improve LeAudio -> HFP call handover

With this patch, HeadsetService will set LeAudio inactive when HFP is
about to handover the call.
This will help to disconnect CISes faster and let SCO creation when
CISes are not there.

Bug: 242908683
Test: atest BluetoothInstrumentationTests
Tag: #feature
Change-Id: I8ad17df6c77141e24674735aa02a9a6d9b585078