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
Merged-In: I8ad17df6c77141e24674735aa02a9a6d9b585078
Change-Id: I8ad17df6c77141e24674735aa02a9a6d9b585078
(cherry picked from commit 2e7636ea)