test: tmpd: Make VpnorRoot the parent of ro/rw/prsv/patch

Previously it represented any one of the ro/rw/prsv/patch directories.
It's better if we can deal with all of them at once, so rework the
abstraction.

In the process, the patch exploits other features of
std::experimental::filesystem to increase readability of the code.

Change-Id: I06000709622dd66945cc88cb5333847c69215dc7
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/test/vpnor/create_pnor_partition_table.cpp b/test/vpnor/create_pnor_partition_table.cpp
index fb371cb..98d474b 100644
--- a/test/vpnor/create_pnor_partition_table.cpp
+++ b/test/vpnor/create_pnor_partition_table.cpp
@@ -1,12 +1,10 @@
 // SPDX-License-Identifier: Apache-2.0
 // Copyright (C) 2018 IBM Corp.
-#include "pnor_partition_table.hpp"
-#include "config.h"
 #include <assert.h>
 #include <string.h>
-#include <vector>
-#include <fstream>
-#include <experimental/filesystem>
+
+#include "config.h"
+#include "pnor_partition_table.hpp"
 
 #include "test/vpnor/tmpd.hpp"
 
@@ -18,15 +16,14 @@
 };
 constexpr auto partitionName = "HBB";
 
-namespace fs = std::experimental::filesystem;
 namespace test = openpower::virtual_pnor::test;
 
 int main()
 {
     test::VpnorRoot root(toc, BLOCK_SIZE);
 
-    const openpower::virtual_pnor::partition::Table table(
-        fs::path{root.path()}, BLOCK_SIZE, PNOR_SIZE);
+    const openpower::virtual_pnor::partition::Table table(root.ro(), BLOCK_SIZE,
+                                                          PNOR_SIZE);
 
     pnor_partition_table expectedTable{};
     expectedTable.data.magic = PARTITION_HEADER_MAGIC;