Fix 4 broken work profile tests

Commit 2953f31b skipped
RunSettingsRoboTests. The tests started failing because
WorkSoundPreferenceController calls UserManager.isUserUnlocked(int) now
which is not implemented in robolectric.

Fixed by adding a wrapper method to AudioHelper.

Fix: 34819603
Test: make RunSettingsRoboTests
Change-Id: Ia79cc4def9442706752f7e7b9a895ffa8150fd9d