PIM-1915 Translations not added to the attribute are not exported

```
Bug fix: yes
Feature addition: no
Backwards compatibility break: yes
Unit test passes: yes
Specs passes: yes
Replaced unit test classes removed: yes
Behat scenario passes: yes
Checkstyle issues: no
ChangeLog updated: no
Documentation PR:
Fixes the following jira:
 - PIM-1915
```
Translation that were not added (in the db) to the attribute were not exported.
This results in shifting in the exported csv.

Futhermore, `default` locale was still set on some attributes in the fixtures althought we dropped it.

Choice was made to pass activated locale codes through the `$context` argument because it's not possible to inject the locale repository into the translation normalizer. The reason for that is that the pim_serializer is injected inside a doctrine event listener (add version listener), thus it creates a circular reference of `doctrine.orm.default_entity_manager` when we try to inject the repository inside the normalizer.

See https://github.com/akeneo/pim-community-dev/issues/658