Kerberos Authentication package doesn't save starting URLs

This was noticed when using Drive against a Nuxeo with the Kerberos Authentication package installed: the login form embedded by Drive doesn't redirect to drive_login.jsp in case of success, instead the Nuxeo web UI is displayed.

This is because the package configuration file kerberos-config.xml badly overrides the plugin configuration Kerberos-authenticator-contrib.xml actually fixed by NXP-16791 to save starting URLs, see https://github.com/nuxeo-archives/nuxeo-platform-login/commit/7b8fdff88adedf05cc74864d8292c6b790bd216c.