NOMDL MNet remote enrolment client: display a button to go back to the course selection

Without this button, the user has to go through the admin menu again,
selecting the same host. This improves the usability when enrolling
local users to multiple remote courses.

mnet/service/enrol/course.php

@@ -192,4 +192,7 @@ if ($usecache) {
                                 get_string('refetch', 'mnetservice_enrol'), 'get');
 }
 
+echo $OUTPUT->single_button(new moodle_url('/mnet/service/enrol/host.php', array('id'=>$host->id)),
+                            get_string('availablecourseson', 'mnetservice_enrol', s($host->hostname)), 'get');
+
 echo $OUTPUT->footer();