Fix prompting - had the logic backwards. The git-cl unit tests actually test the prompting correctly (once they are modified to pass otherwise).

Review URL: http://codereview.chromium.org/6679032

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@77985 0039d316-1c4b-4281-b951-d872f2087c98