[TwigBundle] do not pass a template reference to twig

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
bug #12197 [TwigBundle] do not pass a template reference to twig (Tobion)

This PR was merged into the 2.3 branch.

Discussion
----------

[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.

Commits
-------

7fe33e3 [TwigBundle] do not pass a template reference to twig