Add alternative cockpit "updated" needle

When we have to restart Cockpit during the update, we don't get
the usual "successful" screen after logging back in, we'll have
to match on something indicating an update did happen. I wanted
to use the little icon next to the package count but it seems to
have some kind of problem with anti-aliasing or something, I've
created two needles for it and neither matched on the next run
of the test. So let's match on this "reboot needed" text instead,
I hope it'll always be there when we hit this case.

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

needles/cockpit/cockpit_updates_updated-reboot-20210323.json

@@ -0,0 +1,15 @@
+{
+  "area": [
+    {
+      "width": 56,
+      "ypos": 282,
+      "type": "match",
+      "height": 19,
+      "xpos": 319
+    }
+  ],
+  "properties": [],
+  "tags": [
+    "cockpit_updates_updated"
+  ]
+}