I cannot reproduce the test failures in https://chromiumcodereview.appspot.com/24047003/ but I figure there must be a good reason tear_down_svn had this check so adding it to tear_down_git.

Review URL: https://chromiumcodereview.appspot.com/23437029

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@222785 0039d316-1c4b-4281-b951-d872f2087c98