scripts/nvmf_perf: create results dir early

"measure_*" threads in script use the same results dir
as the results parsing function. To avoid race try to
create results destination directory early.

Change-Id: Ic391a7c2fb3decff64f1fdf51782abb940706d38
Signed-off-by: Karol Latecki <karol.latecki@intel.com>
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/6044
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Paul Luse <paul.e.luse@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>

scripts/perf/nvmf/run_nvmf.py

@@ -957,6 +957,11 @@ if __name__ == "__main__":
 
     target_obj.tgt_start()
 
+    try:
+        os.mkdir(target_results_dir)
+    except FileExistsError:
+        pass
+
     # Poor mans threading
     # Run FIO tests
     for block_size, io_depth, rw in fio_workloads: