AudioManager.testVolume: don't assume index 1 is always valid

Based on permissions, a stream volume index is not always valid.
Remove this assumption from the test by instead using the highest
non-zero value a stream can have for testing the volume adjustment
behaviors.

Bug: 157319908
Test: atest CtsMediaTestCases:android.media.cts.AudioManagerTest#testVolume
Change-Id: I2748eaf2076b4fbe64615bdb0a5fc888f9e35087
1 file changed