Modifies Installation return codes to not return success (0) if an existing version was launched.  Omaha needs to know the correct error result if it is to show the right error message to the user.
Modifies Installation return codes to not return success (0) if an existing version was launched.  Omaha needs to know the correct error result if it is to show the right error message to the user.

R=cpu
BUG=40607
TEST=Over-install trunk/dev channel over a system-level stable install, you should see error code 3


Review URL: http://codereview.chromium.org/1747001

git-svn-id: http://src.chromium.org/svn/trunk/src@45236 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 640743cc72d194106bfe3aeafb4abc953920c018
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser