H5P module locking session after saving

Close session before finishing zip file, which might take substantial time to allow other pages to use session without waiting on the file operation to finish.

h5p.classes.php

@@ -1927,6 +1927,11 @@ Class H5PExport {
       }
     }
 
+    // Close session before finishing zip file, which might take
+    // substantial time to allow other pages to use session without
+    // waiting on the file operation to finish.
+    \core\session\manager::write_close();
+
     // Close zip and remove tmp dir
     $zip->close();
     H5PCore::deleteFileTree($tmpPath);