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/cli/accessory.rb

@@ -14,8 +14,6 @@ class Mrsk::Cli::Accessory < Mrsk::Cli::Base
             execute *MRSK.auditor.record("Booted #{name} accessory"), verbosity: :debug
             execute *accessory.run
           end
-
-          audit_broadcast "Booted accessory #{name}" unless options[:skip_broadcast]
         end
       end
     end