sync: clear auth error on shutdown.
sync: clear auth error on shutdown.

BUG=60814
TEST=Set up sync, enter wrong creds, Cancel, Set up sync again. Notice no error.

Review URL: http://codereview.chromium.org/4211003

git-svn-id: http://src.chromium.org/svn/trunk/src@64351 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 31e4300046a4cef960b19c110ca0eecec352f0f3
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