mpool/base: silence a valgrind warning

by adding a constructor to mca_mpool_base_tree_item_t

Signed-off-by: Gilles Gouaillardet <[email protected]>

Author: ggouaillardet

opal/mca/mpool/base/mpool_base_tree.c

@@ -15,7 +15,7 @@
  * Copyright (c) 2010      IBM Corporation.  All rights reserved.
  * Copyright (c) 2012-2015 Los Alamos National Security, LLC.
  *                         All rights reserved.
- * Copyright (c) 2015      Research Organization for Information Science
+ * Copyright (c) 2015-2018 Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
  * Copyright (c) 2018      Amazon.com, Inc. or its affiliates.  All Rights reserved.
  * $COPYRIGHT$
@@ -43,7 +43,11 @@ static char *leak_msg = NULL;
 static int condition(void *value);
 static void action(void *key, void *value);
 
-OBJ_CLASS_INSTANCE(mca_mpool_base_tree_item_t, opal_free_list_item_t, NULL, NULL);
+static void mpbtcons(mca_mpool_base_tree_item_t *item) {
+    item->key = NULL;
+}
+
+OBJ_CLASS_INSTANCE(mca_mpool_base_tree_item_t, opal_free_list_item_t, mpbtcons, NULL);
 
 /*
  * use globals for the tree and the tree_item free list..