Revert "Revert message bus upgrade"

This reverts commit 47e718f5b24cb2d8b991f5b1a51efe3f79f5f934.

config/initializers/001-redis.rb

@@ -0,0 +1,15 @@
+if Rails.env.development? && ENV['DISCOURSE_FLUSH_REDIS']
+  puts "Flushing redis (development mode)"
+  $redis.flushall
+end
+
+if defined?(PhusionPassenger)
+    PhusionPassenger.on_event(:starting_worker_process) do |forked|
+        if forked
+            Discourse.after_fork
+        else
+            # We're in conservative spawning mode. We don't need to do anything.
+        end
+    end
+end
+