RESTRICT AUTOMERGE AudioManagerTest: skip testVolume for TV

TV devices are connected to audio devices that are typically fixed
or full volume, therefore causing incremental volume changes to be
disabled, but there are no APIs yet to query this, therefore we
skip the testVolume test altogether for TVs.
Also improve assert messages in testVolume.

Bug: 160531287
Fix: 149722142
Test: atest CtsMediaTestCases:android.media.cts.AudioManagerTest#testVolume
Change-Id: I72afbda0cc2b9e501031001e7e4287692b8ea9b5
Merged-In: I72afbda0cc2b9e501031001e7e4287692b8ea9b5
(cherry picked from commit 5cb6288660c9bafdd15c5d25f896ead4ef55e445)
1 file changed