[REF] Fix issue where by mailing urls were always stuck in the origin…

[seamuslee001]

…al language not the overriden language in a multilingual site

Overview

This fixes an issue where by if you are running a multilingual Drupal 8 site with inherit language enabled the mailing urls in a test mailing remain the original language not the language set in the mailing

Before

1. Create a Drupal 8 Site, set it to be multilingual french and English and make sure Drupal is also multilingual, make sure the french url adds /fr onto the end of the base url.
2. Create a new mailing on the English site but set the language of the mailing to be French
3. Send a test email, find that the unsubscribe etc urls go to the site without /fr enabled even tho the mailing is in French

After

Find that the urls are correct.

ping @MikeyMJCO @mlutfy @KarinG

[civibot]

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[KarinG]

Thanks @seamuslee001 - working with a client to reproduce & test.

[seamuslee001]

@KarinG how did you go? @mlutfy just wondering if you have had any capacity to review this (understandable if you haven't)

[mlutfy]

@samuelsov might be interested?

[samuelsov]

Wow, getCurrentLanguage is in fact getDefaultLanguage, obvious isn't it :)

@seamuslee001 I can confirm the bug and that it's fixed by the PR. Thanks!

Ready for merge.

[eileenmcnaughton]

Thanks @samuelsov !