LeAudioService: Do not block API for setVolume call

There is no need to keep API blocked for the whole setVolume operation
especially that it involves AudioManager calls and Native operation.
It is enought to confirm that service accepts the call.

Bug: 302125053
Test: atest LeAudioServiceTest
Tag: #feature
Change-Id: I4a7b757da137d0389928833c1976038eddea8b10