CTS test is not considering the case when the devcie get into SILENT mode by volume down key.

When volume gets down to SILENT mode, added the condition to go to VIBRATE mode or SILENT mode instead of SILENT mode only.

Change-Id: I4ad6302d3d3eba3109e3d0de3060685c9a7013c8
diff --git a/tests/tests/media/src/android/media/cts/AudioManagerTest.java b/tests/tests/media/src/android/media/cts/AudioManagerTest.java
index 3de8a51..cfa9293 100644
--- a/tests/tests/media/src/android/media/cts/AudioManagerTest.java
+++ b/tests/tests/media/src/android/media/cts/AudioManagerTest.java
@@ -575,7 +575,8 @@
                 mAudioManager.setStreamVolume(streams[i], 1, FLAG_SHOW_UI);
                 mAudioManager.adjustStreamVolume(streams[i], ADJUST_LOWER, FLAG_ALLOW_RINGER_MODES);
                 // lowering the volume should have changed the ringer mode
-                assertEquals(RINGER_MODE_VIBRATE, mAudioManager.getRingerMode());
+                assertTrue(mAudioManager.getRingerMode() == RINGER_MODE_VIBRATE ||
+                        mAudioManager.getRingerMode() == RINGER_MODE_SILENT);
                 mAudioManager.adjustStreamVolume(streams[i], ADJUST_LOWER, FLAG_ALLOW_RINGER_MODES);
                 // adjusting the volume to zero should result in either silent or vibrate mode
                 assertTrue(mAudioManager.getRingerMode() == RINGER_MODE_VIBRATE ||