Update platform_Shutdown to catch more error cases.

There have been a few errors from platform_Shutdown that are not properly
populating the reason field. This catches them and fixes a few minor other
issues I hit while testing the change.

TEST=autoserv server/site_tests/platform_Shutdown/control -s -m host
BUG=chromium-os:36221

Change-Id: I509f593de396e8c7147ea0776f09183270b8b761
Reviewed-on: https://gerrit.chromium.org/gerrit/37733
Tested-by: Scott Zawalski <scottz@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Ready: Scott Zawalski <scottz@chromium.org>
Reviewed-by: Scott Zawalski <scottz@chromium.org>
1 file changed