BUGFIX: Correct after_fork semantics

After fork SiteSettings was not getting a new process id,
causing site settings not to refresh properly in unicorn

This code also centralizes the logic

config/initializers/01-redis.rb

@@ -10,10 +10,7 @@ end
 if defined?(PhusionPassenger)
     PhusionPassenger.on_event(:starting_worker_process) do |forked|
         if forked
-            # We're in smart spawning mode.
-            $redis = DiscourseRedis.new
-            Discourse::Application.config.cache_store.reconnect
-            MessageBus.after_fork
+            Discourse.after_fork
         else
             # We're in conservative spawning mode. We don't need to do anything.
         end