Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Zach Robinson:
     Move dashboard client delete logic into ServiceDashboardClientManager ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/22645762 )
     ServiceDashboardClientDiffer accepts dashboard clients, not catalog services ( Travis Unknown )
  David Sabeti and Zach Robinson:
     Remove unused code. ( Travis Unknown )