Revert "Change cleanup phase to only restart the UI instead of rebooting the machine."

There is an issue where platform_Shutdown has a dependency on reboots in cleanup.
Once that is fixed we can reland this commit.

This reverts commit 76552a34a8355cfaa14bb8906f232a57b9df0cc3.

BUG=chromium-os:35150
TEST=instanceof(revert) == True

Change-Id: I1e311bdb7f91df539e90524bb8f79a69fce58c3b
Reviewed-on: https://gerrit.chromium.org/gerrit/35042
Reviewed-by: Chris Sosa <sosa@chromium.org>
Tested-by: Chris Sosa <sosa@chromium.org>
4 files changed