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

```
Bug fix: yes
Feature addition: no
Backwards compatibility break: yes
Unit test passes: no
Specs passes: no (pending examples)
Replaced unit test classes removed: not yet
Behat scenario passes: normally
Checkstyle issues: maybe
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.

See https://github.com/akeneo/pim-community-dev/issues/658