Mark A/B Boot success before committing checkpoint

This marks the slot as successful within commitChanges, increasing the
available roll back window significantly.

Test: When taking an update on a checkpoint enabled device, it
      marks the slot as successful just before committing the
      checkpoint. Visible in logs as call to vdc commitChanges,
      followed by "Marked slot as booted succesfully."
Bug: 123260515
Change-Id: If71fcde57b3bdee2cfaabb590f123a2d00da3228
1 file changed