MDL-9028 prelogout_hook() is never executed in login/logout.php; patch by Inaki Arenaza; merged from MOODLE_18_STABLE

login/logout.php

@@ -6,12 +6,6 @@
     // can be overriden by auth plugins
     $redirect = $CFG->wwwroot.'/';
 
-    $authsequence = explode(',', $CFG->auth); // auths, in sequence
-    foreach($authsequence as $authname) {
-        $authplugin = get_auth_plugin($authname);
-        $authplugin->prelogin_hook();
-    }
-
     $sesskey = optional_param('sesskey', '__notpresent__', PARAM_RAW); // we want not null default to prevent required sesskey warning
 
     if (!confirm_sesskey($sesskey)) {
@@ -21,6 +15,12 @@
         die;
     }
 
+    $authsequence = explode(',', $CFG->auth); // auths, in sequence
+    foreach($authsequence as $authname) {
+        $authplugin = get_auth_plugin($authname);
+        $authplugin->prelogout_hook();
+    }
+
     require_logout();
 
     redirect($redirect);