LPS-49013

Hi Maté,

I sent this pull (https://github.com/ealonso/liferay-portal/pull/242) to @ealonso. He asked to me to retest with his SF and resend to you. 

**Root cause of problem:**
* JournalArticleTrashHandler.isInTrash(long classPK) expects "resourcePrimKey" as input
* At BaseStagedModelDataHandler the getPrimaryKeyObj is used for JournalArticle ('id_' instead 'resourceprimkey') so no JournalArticle is obtained from database

**Solution:**
1. Replace getPrimaryKeyObj() with getTrashEntryClassPK(). 
This function returns correct resourcePrimKey for JournalArticle and primaryKey for rest of objects.
2. The function belongs to TrashedModel, so instead checking (trashHandler != null), I replace it with (stagedModel instanceof TrashedModel). 
All objects with trashHandler must inherit TrashedModel, so check is equivalent.