Ensure publishing a layer already published does nothing

Just in case two users go to publish the same layer at around the same
time, avoid saving the record for a user who tries to publishes it after
the first time.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

TODO

@@ -6,8 +6,6 @@ TODO:
 
 - we might consider adding a link to the all layers and all recipes tables from the layer details page
 
-* Ensure publishing a published layer doesn't do anything
-
 * Need an "About" section descriptibing what the site is for
 * Need an admin contact in footer
 * Some columns are a bit crushed

layerindex/views.py

@@ -77,8 +77,9 @@ def publish(request, name):
 
 def _statuschange(request, name, newstatus):
     w = get_object_or_404(LayerItem, name=name)
-    w.change_status(newstatus, request.user.username)
-    w.save()
+    if w.status != newstatus:
+        w.change_status(newstatus, request.user.username)
+        w.save()
     return HttpResponseRedirect(reverse('layer_item', args=(name,)))
 
 class LayerListView(ListView):