CEC: Make persisting volume control flag configurable

Add an internal method for changes to the volume flag which doesn't
presist the value. External API calls to change the volume feature flag
will continue to be persisted in setHdmiCecVolumeControlEnabled(boolean).

All internal calls to setHdmiCecVolumeControlEnabled change to the
internal method.

Bug: 158307190
Test: atest HdmiControlService
Change-Id: I2ac4a70db01752f214dd87ca17174b81acddb1dd