Add post-deploy and post-rollback hooks

These replace the custom audit_broadcast_cmd code. An additional env
variable MRSK_RUNTIME is passed to them.

The audit broadcast after booting an accessory has been removed.

lib/mrsk/configuration.rb

@@ -157,10 +157,6 @@ class Mrsk::Configuration
   end
 
 
-  def audit_broadcast_cmd
-    raw_config.audit_broadcast_cmd
-  end
-
   def healthcheck
     { "path" => "/up", "port" => 3000, "max_attempts" => 7 }.merge(raw_config.healthcheck || {})
   end