dpm: correctly handle procs_cutoff in ompi_dpm_connect_accept()

this commit includes missing bits from open-mpi/ompi@213b2abde4

ompi/dpm/dpm.c

@@ -183,7 +183,7 @@ int ompi_dpm_connect_accept(ompi_communicator_t *comm, int root,
             }
             opal_argv_append_nosize(&members, nstring);
             free(nstring);
-            if (NULL == (nstring = (char*)opal_pmix.get_nspace(proc_list[i]->super.proc_name.jobid))) {
+            if (NULL == (nstring = (char*)opal_pmix.get_nspace(proc_name.jobid))) {
                 opal_argv_free(members);
                 free (proc_list);
                 return OMPI_ERR_NOT_SUPPORTED;