[TwigBundle] do not pass a template reference to twig

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

twig does not know about template references and only expects a string.
this commit also fixes that name parsing and locating was called twice for nonexistent templates.
and it does change in 2.x, removing the string casting