SAK-27500 Return to correct site after login.

When the login choice page is enabled the xlogin route would always take a user back to their MyWorkspace after login. This fixes it so that it takes them back to the original URL entered into the browser.

git-svn-id: https://source.sakaiproject.org/svn/portal/trunk@311156 66ffb92e-73f9-0310-93c1-f5514f145a0a