Fix CarVolumeServiceTest failure.

1. VolumeLimit test failure
 - The min config value is always 0 in the new vhal. So the test for min
   volume is removed.

2. testSuppressVolumeUI failure
 - The reason is the car service code runs in the same process with the
   test. When the test waits for a callback, it blocked the main thread
   on which the Handler is running
 - Moved the Handler in the car volume controller to a handler thread.

Fix: 36614115

Test: runtest -x packages/services/Car/tests/carservice_test/ \
       -c com.android.car.test.CarVolumeServiceTest

(cherry picked from commit 543ef8915362454aa2ea13b61ebe9f6d21a8070c)

Change-Id: I5a7fa4cf232e39090288d6cdc5379f00295e6ee5
3 files changed