fix: OMPI_ERR_CONNECTION_FAILED available in v1.5, unavailable in trunk

This commit was SVN r25459.

ompi/mca/mtl/mxm/mtl_mxm.c

@@ -258,7 +258,7 @@ int ompi_mtl_mxm_add_procs(struct mca_mtl_base_module_t *mtl, size_t nprocs,
                           mxm_error_string(conn_reqs[i].error));
             }
         }
-        rc = OMPI_ERR_CONNECTION_FAILED;
+        rc = OMPI_ERROR;
         goto bail;
     }