hudson.model.Failure class doesn't work if the caller doesn't have "overall/read" permission.

This is observed with OpenID plugin authentication problem. The plugin throws the Failure object in an attempt to render the error page, but Jenkins doesn't allow requests to be routed to the error.jelly if the overall/read permission is not granted.

The fix is pretty trivial in Jenkins.getTarget() but I need to write a test case as well and I don't have time right now, so I'm filing it instead.