Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Max Brunsfeld:
     Restore old behavior of App#current_droplet ( Travis created: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31284638 )
  Michael Fraenkel:
     Dont create/update buildpack entry when uploading blobs fails ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31282903 )
  Simon Leung:
     Eager-load domains in StagedAppsQuer ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31276076 )
     Fix error in App#detected_start_command ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31267493 )
  Leo Rossignac-Milon:
     Add Roodi Gem - Services pre-commit hook ( Travis Failed: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31270835 )
  Raina Masand:
     Added documentation for /v2/spaces/:guid/service_instances?return_user_provided_service_instances ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31268958 )
  Graeme Davison:
     Use Rack access logging appropriately ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31195055 )

Signed-off-by: Simon Leung <leungs@us.ibm.com>