LPS-51356 Reindexing JournalArticles in background on DDMStructure update

Hi Dani,

This is the issue I had some questions earlier. It moves the reindexing of JournalArticles when updating DDMStructure. I limited this logic when the indexer is instance of JournalArticleIndexer to do not break other logics as Máté told me that in some places there's a logic built on the reindexing, but for this scenario I didn't find any. So I modified this part only.

Regards,
Vilmos