Add commitChanges for signaling checkpointing end

This adds a place to call commitCheckpoint from java
so the framework can inform the checkpointing system
of a successful boot.

Test: vdc checkpoint startCheckpoint 5
      checkpoint file should disapear on boot
Bug: 111020314

Change-Id: I6f9968a55f0bd3557918a25eb6569ca333408da6
3 files changed