Logged In: YES 
user_id=469548

Another patch to fix two issues:

* Apparently HEAD needs a bunch more attributes on the
Client class than maint-0-7, so I've added those.
* The previous patch didn't work when a tracker overrides
the action used for logging in (as we do, for LDAP
authentication). This patch factors out a get_action_class
method from handle_action, and determine_user now calls it
to determine what class it should call verifyLogin on.