fix saml_login login.url

login.url URL is used to generate the passcode link (https://github.com/cloudfoundry/login-server/blob/master/saml-login-server/src/main/webapp/WEB-INF/spring-servlet.xml#L478).

but uaa doesn't response to /passcode, saml-login does: 

    nicholask@utility:~/cf/login-server$ git grep '/passcode'
    saml-login-server/src/main/java/org/cloudfoundry/identity/uaa/login/PasscodeController.java:    @RequestMapping(value = { "/passcode" }, method = RequestMeth
    saml-login-server/src/main/webapp/WEB-INF/spring-servlet.xml:                                   <constructor-arg name="text" value="One Time Code (Get one at