pstat linux: close the files

as reported by Coverity with CID 71983

opal/mca/pstat/linux/pstat_linux_module.c

@@ -12,6 +12,8 @@
  * Copyright (c) 2006-2015 Cisco Systems, Inc.  All rights reserved.
  * Copyright (c) 2013      Los Alamos National Security, LLC.  All rights reserved.
  * Copyright (c) 2013      Intel, Inc.  All rights reserved.
+ * Copyright (c) 2015      Research Organization for Information Science
+ *                         and Technology (RIST). All rights reserved.
  *
  * $COPYRIGHT$
  * 
@@ -412,6 +414,7 @@ static int query(pid_t pid,
             opal_list_append(&nstats->diskstats, &ds->super);
             opal_argv_free(fields);
         }
+        fclose(fp);
 
     netstats:
         /* look for the netstats file */