AudioService: evaluate permissions for min stream index

Make AudioManager.getStreamMinVolume(stream) return the lowest
index the caller of this API can set or adjust the volume to
based on the caller's permissions.

Bug: 137015603
Bug: 157319908
Test: atest CtsMediaTestCases:android.media.cts.AudioManagerTest#testVolume
Change-Id: Ie306bd652c2b5ab4d789cafbb141ea530fb1e650