Fix minor MPI thread memory leak / fix valgrind still-reachable warning.

cmr=v1.7.5:reviewer=brbarret:subject=Fix minor MPI thread memory leak

This commit was SVN r30072.

ompi/runtime/ompi_mpi_finalize.c

@@ -10,7 +10,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2006-2012 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2006-2013 Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2006-2012 Los Alamos National Security, LLC.  All rights
  *                         reserved. 
  * Copyright (c) 2006      University of Houston. All rights reserved.
@@ -398,6 +398,11 @@ int ompi_mpi_finalize(void)
         return ret;
     }
 
+    if (NULL != ompi_mpi_main_thread) {
+        OBJ_RELEASE(ompi_mpi_main_thread);
+        ompi_mpi_main_thread = NULL;
+    }
+
     /* Leave the RTE */
 
     if (OMPI_SUCCESS != (ret = ompi_rte_finalize())) {