Preserve the rollback-version file as part of powerwash.

Also as part of this CL I am saving and preserving the log of clobber-state.

BUG=chromium:252589
TEST=Ran powerwash after an AU rollback and check file was preserved and
other files were preseved if file was missing.

Change-Id: Ifebc168b41c42347995e0e10c825d2cdc06c9aa0
Reviewed-on: https://gerrit.chromium.org/gerrit/59524
Commit-Queue: Chris Sosa <sosa@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
1 file changed