node preview translation needs to get translation of entity if it hasTranslation

with just core:
Steps to reproduce: French term label in German preview

1. Install drupal in French
2. add Deutsch
3. enable content_translation
4. edit the article content type, enable translation
5. make sure the content type has a taxonomy term reference to tags vocabulary
6. enable translation of tags vocabulary
7. add a term such as Français, translate it to Deutsch
8. select add an article content and select the term Français
9. press the preview button
10. tags label shows up as Français
11. change the language prefix of that preview page to de (deutsch)
12. taxonomy term shows up as Français, expected Deutsch

see screenshots
Français preview

Deutsch preview

OR

OR, preferred testing method: use the entity_translation_unified_form module:

1. Install the entity_translation_unified_form module (latest dev release) (screenshot)
2. configure default language and another language or as many languages as you like.
3. refer to the README in the etuf module on configuration.
4. Can skip this step: apply the etuf sbs patch to the entity_translation_unified_form module if you want to see it work like this screenshot for this step: (VERY COOL).
5. Press the drupal core provided preview button, then switch to the other language.

With core patch enabled, correct language preview shows up, without core patch, default language shows up regardless of what the interface language is