MDL-73245 cache: Fix bug with session lock debugging

When session lock debugging and read only sessions deubgging are both
enabled, session lock debugging becomes moot. This patch causes
the session lock deubgging code to exit early if read only sessions
debugging is enabled.

lib/classes/session/manager.php

@@ -1310,7 +1310,9 @@ public static function update_recent_session_locks($sessionlock) {
             return;
         }
 
-        if (defined('READ_ONLY_SESSION') && READ_ONLY_SESSION && !empty($CFG->enable_read_only_sessions)) {
+        $readonlysession = defined('READ_ONLY_SESSION') && READ_ONLY_SESSION;
+        $readonlydebugging = !empty($CFG->enable_read_only_sessions) || !empty($CFG->enable_read_only_sessions_debug);
+        if ($readonlysession && $readonlydebugging) {
             return;
         }