[TaxonomyPlugin] Labels for other languages should default to the English label

1. Create a test taxonomy with en, de and es locales
2. Create an entry 'Test One' in English and also provide a name 'Prufen Eins' for German language
3. Create an entry 'Test Two' in English. Do not provide names for other languages
4. Create an entry 'Test Three', in English. Do not save and create a name for Spanish as 'Test Three Espaniol'(this issue is explained in CMS-15350). Do not provide names for other languages
5. Now go back to Content view, create a new translated folder with German language and create a test document
6. Open the document and try to select keys
7. First folder name is displayed correctly since a German name was provided
8. Second folder name displayed is 'test-two' while the client expects this to default to the English name 'Test Two'
9. Third folder name displayed is 'test-three-espaniol', while the client expects this to default to the English name 'Test Three'

The expectation is to display the English name as the default label when labels for other languages are not provided.