correctly handle transforming settings into useful datastructure

app/controllers/concerns/requires_whitelisted_monitoring_client.rb

@@ -14,6 +14,10 @@ module RequiresWhitelistedMonitoringClient
     Settings.monitoring.ip_whitelist.any? { |e| e.include?(Gitlab::RequestContext.client_ip) }
   end
 
+  def ip_whitelist
+    @ip_whitelist ||= Settings.monitoring.ip_whitelist.map(&IPAddr.method(:new))
+  end
+
   def token_valid?
     token = params[:token].presence || request.headers['TOKEN']
     token.present? &&

config/initializers/1_settings.rb

@@ -499,7 +499,6 @@ Settings.webpack.dev_server['port']    ||= 3808
 #
 Settings['monitoring'] ||= Settingslogic.new({})
 Settings.monitoring['ip_whitelist'] ||= %w{127.0.0.1/8}
-Settings.monitoring.ip_whitelist.map!(&IPAddr.method(:new))
 
 #
 # Prometheus metrics settings