Enable/disable delayed jobs in the secrets file

While this is not a secret and in theory should be in a file under
version control, currently the CONSUL installer disables delayed jobs by
default, meaning we were keeping two versions of the delayed jobs
configuration file, and some existing configurations have their settings
defined in a file in capistrano's `shared` folder.

So we're moving existing settings to the secrets file.

lib/tasks/secrets.rake

@@ -1,10 +1,11 @@
 namespace :secrets do
-  desc "Add SMTP and SSL settings to secrets.yml"
-  task smtp_and_ssl: :environment do
+  desc "Add SMTP, SSL and delay jobs settings to secrets.yml"
+  task smtp_ssl_and_delay_jobs: :environment do
     current_settings = {
       "mailer_delivery_method" => ActionMailer::Base.delivery_method.to_s,
       "smtp_settings"          => ActionMailer::Base.smtp_settings.stringify_keys,
-      "force_ssl"              => Rails.application.config.force_ssl
+      "force_ssl"              => Rails.application.config.force_ssl,
+      "delay_jobs"             => Delayed::Worker.delay_jobs
     }
 
     settings_to_add = current_settings.select do |name, _|