plm_slurm_module.c: don't leave the extra fd to /dev/null open

Prior to r29058, this same logic was in place (i.e., ensure that the
extra fd to /dev/null is closed).  It looks like it was accidentally
removed in the ORTE conversion to the state machine in r29058.

This ''might'' have something to do with many hangs that we're seeing
in Cisco MTT with jobs that exhibit failure (e.g., call MPI_ABORT)...?

cmr=v1.8.2:reviewer=rhc

This commit was SVN r31469.

The following SVN revision numbers were found above:
  r29058 --> open-mpi/ompi@a200e4f865

orte/mca/plm/slurm/plm_slurm_module.c

@@ -9,7 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
- * Copyright (c) 2006-2007 Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2006-2014 Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2007-2012 Los Alamos National Security, LLC.  All rights
  *                         reserved. 
  * Copyright (c) 2014      Intel Corporation.  All rights reserved.
@@ -642,6 +642,11 @@ static int plm_slurm_start_proc(int argc, char **argv, char **env,
                 dup2(fd,1);
                 dup2(fd,2);
             }
+
+            /* Don't leave the extra fd to /dev/null open */
+            if (fd > 2) {
+                close(fd);
+            }
         }
 
         /* get the srun process out of orterun's process group so that