MDL-9399 auth/shibboleth: ensure we load enrolments

Most of this code should be replaced with complete_user_login() but it
does a few odd things, so we'll play it safe for now, specially since
I don't have a Shib setup to test...

auth/shibboleth/index.php

@@ -72,6 +72,7 @@
                 }
             }
 
+            check_enrolment_plugins($USER);
             load_all_capabilities();     /// This is what lets the user do anything on the site  :-)
 
             redirect($urltogo);