Check jinja templates for syntax error (#10667)

Allow to fail early (pre-commit time) for jinja error, rather than
waiting until executing the playbook and the invalid template.

I could not find a simple jinja pre-commit hook in the wild.

tests/scripts/check-templates.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python
+
+import sys
+from jinja2 import Environment
+
+env = Environment()
+for template in sys.argv[1:]:
+    with open(template) as t:
+        env.parse(t.read())