Pull submodules for ms-testing-suite (refs #24069).

tester.py

@@ -233,7 +233,10 @@ class Tester():
             if os.path.exists(ms_path):
                 log('Updating ms-testing-suite in "%s".' % ms_path)
                 os.chdir(ms_path)
-                subprocess.check_call(['git', 'pull'])
+                # TODO:
+                # subprocess.check_call(['git', 'checkout', 'stable'])
+                subprocess.check_call(['git', 'pull', '--recurse-submodules'])
+                subprocess.check_call(['git', 'submodule', 'update', '--recursive'])
                 os.chdir(self.root_dir)
             else:
                 log('Cloning ms-testing-suite in "%s".' % ms_path)