don't need standalone pmix test

tests/ssg-pmix-test.c

-/*
- * Copyright (c) 2016 UChicago Argonne, LLC
- *
- * See COPYRIGHT in top-level directory.
- */
-
-#include <ssg-config.h>
-
-#include <unistd.h>
-#include <stdio.h>
-#include <string.h>
-#include <assert.h>
-
-#include <margo.h>
-
-#include <pmix.h>
-
-int main(int argc, char *argv[])
-{
-    pmix_proc_t proc_info;
-    pmix_status_t ret;
-
-    ret = PMIx_Init(&proc_info, NULL, 0);
-    assert(ret == PMIX_SUCCESS);
-
-    return 0;
-}