Silence warning

Refs trac:4040

This commit was SVN r30105.

The following Trac tickets were found above:
  Ticket 4040 --> https://svn.open-mpi.org/trac/ompi/ticket/4040

ompi/mca/mpool/base/mpool_base_tree.c

@@ -99,6 +99,7 @@ int mca_mpool_base_tree_fini(void)
     OBJ_DESTRUCT(&mca_mpool_base_tree);
     OBJ_DESTRUCT(&mca_mpool_base_tree_item_free_list);
     OBJ_DESTRUCT(&tree_lock);
+    return OMPI_SUCCESS;
 }
 
 /*