Passing the email address used to connect to Rietveld on the command
line is useful for testing purposes, in particular with a test server.

BUG=331123

Review URL: https://codereview.chromium.org/122583003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@244017 0039d316-1c4b-4281-b951-d872f2087c98