AudioManager: route hasAudioFocus() through manager

AudioService API should go through its manager, to avoid exposing
interface through AIDL.

Bug: 416963897
Flag: android.media.audio.audio_focus_desktop
Test: atest CtsPackageInstallTestCases:android.packageinstaller.install.cts.InstallConstraintsTest#testCheckInstallConstraints_AppIsInteracting
Change-Id: I4d2416b506facb77361bad7b5bba1117326db2fb