Add variant GDM needle for missing Fedora logo

Fedora logo is missing from GDM in today's Rawhide. Not going
all the way and making this a soft fail as the bug is known and
should be fixed soon, I'll take the needle out again then.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/gnome/login_gdm-nologo-20190211.json

@@ -0,0 +1,18 @@
+{
+  "area": [
+    {
+      "height": 19,
+      "xpos": 337,
+      "width": 67,
+      "type": "match",
+      "ypos": 419
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "DESKTOP-gnome",
+    "graphical_login",
+    "graphical_login_gdm_nologo",
+    "login_screen"
+  ]
+}