ERP5Workflow: fix if/elif/else order in Folder.py

This avoid to raise NotImplementedError in _initBTree when _folder_handler
is a string containing, for example 'CMFBTreeFolderHandler'.

product/ERP5Type/Core/Folder.py

@@ -745,10 +745,11 @@ class Folder(CopyContainer, CMFBTreeFolder, CMFHBTreeFolder,
   def _initBTrees(self):
     if self._folder_handler == HBTREE_HANDLER:
       return CMFHBTreeFolder._initBTrees(self)
-    elif self._folder_handler == BTREE_HANDLER:
-      return CMFBTreeFolder._initBTrees(self)
-    else:
+    elif self._folder_handler == PERSISTENT_MAPPING_HANDLER:
       raise NotImplementedError
+    else:
+      return CMFBTreeFolder._initBTrees(self)
+
 
   def hashId(self, id):
     """Return a hash of id