Rename cookie.

Fix unused alias.

firmware/lib/firmware/application.ex

@@ -22,7 +22,7 @@ defmodule Firmware.Application do
   # List all child processes to be supervised
   def children(:host) do
     {:ok, _} = Node.start(:"host@0.0.0.0")
-    Node.set_cookie(:testcookie)
+    Node.set_cookie(:tastycookie)
     true = Node.connect(:"esrom@esrom.lan")
     []
   end

firmware/mix.exs

@@ -63,7 +63,7 @@ defmodule Firmware.MixProject do
   def release do
     [
       overwrite: true,
-      cookie: "testcookie",
+      cookie: "tastycookie",
       include_erts: &Nerves.Release.erts/0,
       steps: [&Nerves.Release.init/1, :assemble]
     ]