Copy setup.exe rather than moving it since it is created outside of the target directory heirarchy (regression introduced in r75899).

BUG=82424
TEST=Install system-level Chrome as some admin user X.  Switch to admin user Y and try to uninstall.
R=robertshield@chromium.org

Review URL: http://codereview.chromium.org/7011018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@85159 0039d316-1c4b-4281-b951-d872f2087c98