Regsister ClockEventController listeners in preview

Add a isPreview member to ClockEventController to disable the event
callbacks that shouldn't fire as normal in the preview context. This
also changes some of the logs in ClockEventController.

Bug: 437833979
Test: Tested preview behavior on device
Flag: NONE Minor change to clock preview behavior
Change-Id: Ifd8f4587d3bb313a635614d3c79dcc71ba24ec4a