Revert "Products.CMFActivity.ActivityTool: Remove dependency on portal_catalog owner."

This reverts commit 77b3f202.
For some obscure reason, this affects unit tests related to inventory
unit conversion. There seems to be too much code to cleanup to keep this
patch for now, so drop it.

product/CMFActivity/ActivityTool.py

@@ -1285,7 +1285,10 @@ class ActivityTool (BaseTool):
           self.setupCurrentSkin(self.REQUEST)
           old_sm = getSecurityManager()
           try:
-            newSecurityManager(self.REQUEST, system_user)
+            # get owner of portal_catalog, so normally we should be able to
+            # have the permission to invoke all activities
+            user = self.portal_catalog.getWrappedOwner()
+            newSecurityManager(self.REQUEST, user)
 
             currentNode = getCurrentNode()
             self.registerNode(currentNode)