Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Graeme Davison and Zach Robinson:
     Improve app state error message. ( Travis created: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/30125176 )
  James Myers:
     Revert "Use larger quotas when staging apps with Diego" ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/30120961 )