These will come in handy when testing code that interacts with
multiple gerrit servers (like chromite).

BUG=
R=vadimsh@chromium.org

Review URL: https://codereview.chromium.org/23620021

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@221051 0039d316-1c4b-4281-b951-d872f2087c98