mpit: fix coverity issues

CID 1047284 Uninitialized scalar variable (UNINIT)
CID 1047285 Uninitialized scalar variable (UNINIT)
CID 1047286 Uninitialized scalar variable (UNINIT)

If a performance variable session has no handles we should be returning MPI_SUCCESS
for MPI_T_pvar_start, MPI_T_pvar_stop, and MPI_T_pvar_reset. The code was returning
an unitialized value. This commit also updates the error code to return the proper
error on failure.

Signed-off-by: Nathan Hjelm <hjelmn@me.com>

ompi/mpi/tool/mpit_common.c

@@ -1,6 +1,6 @@
 /* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
- * Copyright (c) 2012-2013 Los Alamos National Security, LLC. All rights
+ * Copyright (c) 2012-2015 Los Alamos National Security, LLC. All rights
  *                         reserved.
  * Copyright (c) 2015      Research Organization for Information Science
  *                         and Technology (RIST). All rights reserved.
@@ -80,6 +80,11 @@ int ompit_var_type_to_datatype (mca_base_var_type_t type, MPI_Datatype *datatype
 
 int ompit_opal_to_mpit_error (int rc)
 {
+    if (rc >= 0) {
+        /* Already an MPI error (always >= 0) */
+        return rc;
+    }
+
     switch (rc) {
     case OPAL_SUCCESS:
         return MPI_SUCCESS;

ompi/mpi/tool/pvar_reset.c

@@ -1,6 +1,6 @@
 /* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil -*- */
 /*
- * Copyright (c) 2012-2013 Los Alamos National Security, LLC. All rights
+ * Copyright (c) 2012-2015 Los Alamos National Security, LLC. All rights
  *                         reserved.
  * Copyright (c) 2014 Cisco Systems, Inc.  All rights reserved.
  * $COPYRIGHT$
@@ -23,7 +23,7 @@
 
 int MPI_T_pvar_reset(MPI_T_pvar_session session, MPI_T_pvar_handle handle)
 {
-    int ret;
+    int ret = MPI_SUCCESS;
 
     if (!mpit_is_initialized ()) {
         return MPI_T_ERR_NOT_INITIALIZED;

ompi/mpi/tool/pvar_start.c

@@ -32,7 +32,7 @@ static int pvar_handle_start (mca_base_pvar_handle_t *handle)
 
 int MPI_T_pvar_start(MPI_T_pvar_session session, MPI_T_pvar_handle handle)
 {
-    int ret;
+    int ret = MPI_SUCCESS;
 
     if (!mpit_is_initialized ()) {
         return MPI_T_ERR_NOT_INITIALIZED;

ompi/mpi/tool/pvar_stop.c

@@ -32,7 +32,7 @@ static int pvar_handle_stop (mca_base_pvar_handle_t *handle)
 
 int MPI_T_pvar_stop(MPI_T_pvar_session session, MPI_T_pvar_handle handle)
 {
-    int ret;
+    int ret = MPI_SUCCESS;
 
     if (!mpit_is_initialized ()) {
         return MPI_T_ERR_NOT_INITIALIZED;