Add new 'GNOME clean desktop' needle for transparent top bar

The GNOME top bar is now transparent in Rawhide, which broke the
'clean desktop' needle. It also means it'll break every time
the background changes, from now on :( Update the needle.

needles/gnome/desktop_clean-20170616.json

@@ -0,0 +1,25 @@
+{
+  "properties": [],
+  "area": [
+    {
+      "type": "match",
+      "width": 67,
+      "xpos": 9,
+      "height": 15,
+      "ypos": 7
+    },
+    {
+      "type": "match",
+      "xpos": 970,
+      "width": 43,
+      "height": 18,
+      "ypos": 4
+    }
+  ],
+  "tags": [
+    "DESKTOP-gnome",
+    "ENV-DISTRI-fedora",
+    "LANGUAGE-english",
+    "graphical_desktop_clean"
+  ]
+}