Revert "Add synchronized lock for ringback playing start/stop request to avoid"

This reverts commit 7b6c9ba0b8b712d008009b323d5a25ebb4dc6ed1.

Reason for revert: seems to be the reason for test break b/276142299

Change-Id: I552292e7addc4f4b20241d6757b40c870fc359e1
2 files changed