Switch exit status from 77 (try again later) back to 12/13 (errors).

When driving an update from KeystoneRegistration, Chrome sees 77 as success.
This causes the about page to say that an update was successfully installed
and offer the option to relaunch. When the user clicks Relaunch, Chrome quits
and the same old version restarts and starts trying to apply an update again.
This seems kind of glitchy.

I'm switching back to the failure codes, because those are properly reported
in the UI. In the future, I can make keystone_glue.mm check for the
.want_full_installer file when update installation fails and silently retry
installation once, for a seamless "error 12"-free experience.

BUG=54047,303280
TBR=thakis

Review URL: https://codereview.chromium.org/121673003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243035 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243035