Fix warnings in instance code

We were never checking the return value from PMIX_UNLOAD and
were not properly checking against GROUP_NULL.

Signed-off-by: Brian Barrett <bbarrett@amazon.com>

Author: bwbarrett

ompi/instance/instance.c

@@ -949,6 +949,11 @@ static void ompi_instance_get_num_psets_complete (pmix_status_t status,
                               &info[n].value,
                               (void **)&num_pmix_psets,
                               &sz);
+            if (rc != PMIX_SUCCESS) {
+                opal_argv_free (ompi_mpi_instance_pmix_psets);
+                ompi_mpi_instance_pmix_psets = NULL;
+                goto done;
+            }
             if (num_pmix_psets != ompi_mpi_instance_num_pmix_psets) {
                 opal_argv_free (ompi_mpi_instance_pmix_psets);
                 ompi_mpi_instance_pmix_psets = NULL;
@@ -962,12 +967,18 @@ static void ompi_instance_get_num_psets_complete (pmix_status_t status,
                               &info[n].value,
                               (void **)&pset_names,
                               &sz);
+            if (rc != PMIX_SUCCESS) {
+                opal_argv_free (ompi_mpi_instance_pmix_psets);
+                ompi_mpi_instance_pmix_psets = NULL;
+                goto done;
+            }
             ompi_mpi_instance_pmix_psets = opal_argv_split (pset_names, ',');
             ompi_mpi_instance_num_pmix_psets = opal_argv_count (ompi_mpi_instance_pmix_psets);
             free(pset_names);
         }
     }
 
+done:
     if (NULL != release_fn) {
         release_fn(release_cbdata);
     }
@@ -1258,7 +1269,10 @@ static int ompi_instance_get_pmix_pset_size (ompi_instance_t *instance, const ch
 
 int ompi_group_from_pset (ompi_instance_t *instance, const char *pset_name, ompi_group_t **group_out)
 {
-    if (group_out == MPI_GROUP_NULL) {
+    if (NULL == group_out) {
+        return OMPI_ERR_BAD_PARAM;
+    }
+    if (*group_out == MPI_GROUP_NULL) {
         return OMPI_ERR_BAD_PARAM;
     }