tests: Validate that JSON deflattening fixed nested json pseudo-protocol strings

Sheepdog and possibly others use nested objects for network server and
thus could be specified in a way that libvirt would not parse.

Validates that https://bugzilla.redhat.com/show_bug.cgi?id=1464821
is fixed properly.

tests/virjsondata/deflatten-qemu-sheepdog-in.json

@@ -0,0 +1,11 @@
+{
+    "driver": "raw",
+    "file": {
+        "server.host": "10.10.10.10",
+        "server.port": "7000",
+        "tag": "",
+        "driver": "sheepdog",
+        "server.type": "inet",
+        "vdi": "Alice"
+    }
+}

tests/virjsondata/deflatten-qemu-sheepdog-out.json

@@ -0,0 +1,13 @@
+{
+  "driver": "raw",
+  "file": {
+    "server": {
+      "host": "10.10.10.10",
+      "port": "7000",
+      "type": "inet"
+    },
+    "tag": "",
+    "driver": "sheepdog",
+    "vdi": "Alice"
+  }
+}