AudioService: fix NOTIFICATION unmuted while in silent/vibrate mode

  Fix support of AudioManager.FLAG_ALLOW_RINGER_MODES which enables
the change of ringer mode in response to the unmuting of a stream
currently muted by the ringer mode.
  When this flag is not present, the unmuting of a muted stream
is not allowed, and that call shouldn't change the ringer mode.
  This prevents entering situations where NOTIFICATION is unmuted
but the ringer mode is VIBRATE or SILENT.

Bug: 278661956
Test: atest CtsMediaAudioTestCases:android.media.audio.cts.AudioManagerTest#testAdjustUnmuteNotificationInSilent
Test: atest CtsMediaAudioTestCases:android.media.audio.cts.AudioManagerTest#testAdjustUnmuteNotificationInVibrate
Change-Id: Ib1306be48ba61a0294e12e3bf7ac74fb54a0bd6c