Add a message in the fullstack Vagrantfile also.

vagrant/release/fullstack/Vagrantfile

@@ -9,6 +9,8 @@ CPU_COUNT = 2
 # to a name and a file path, which are used for retrieving
 # a Vagrant box from the internet.
 openedx_releases = {
+  # Note: the devstack and fullstack boxes differ, because devstack had an issue
+  # that needed fixing, but it didn't affect fullstack.
   "named-release/dogwood" => {
     :name => "dogwood-fullstack-rc2", :file => "20151221-dogwood-fullstack-rc2.box",
   },