Merge pull request #2440 from fawhgb/rm-fileplan-caching-issue

Fixes the caching issue by returning a copy of the set instead of the Set

amps/ags/rm-community/rm-community-repo/source/java/org/alfresco/module/org_alfresco_module_rm/fileplan/FilePlanServiceImpl.java

@@ -219,7 +219,7 @@ public boolean handle(Pair<Long, NodeRef> nodePair)
         }
         else
         {
-            return rmContainerCacheManager.get(storeRef);
+            return new HashSet<>(rmContainerCacheManager.get(storeRef));
         }
 
         return results;