Focus keywords in combination with l10nmgr

[RinyVT]

• [X] I've read and understood the contribution guidelines.
• [X] I've searched for any related issues and avoided creating a duplicate issue.

Please give us a description of what happened.

It has been reported that the structure of tx_yoastseo_related_focuskeyword, based on pid+sys_language_uid+uid_foreign+tablenames does not work correctly with the extension l10nmgr.

This needs to be investigated.

Please describe what you expected to happen and why.

Correct import and export functionality with l10nmgr