Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Maria Shaldibina and Onsi Fakhouri:
     Remove unnecessary logging in HM9000Respondent ( Travis created: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12155595 )
  Julz Friedman and Phan Le:
     Added API documentation for posting an admin buildpack ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12155326 )
     Added API documentation for posting an admin and remove key from external API ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12154899 )
     Added documentation of default delete behaviour to API specs ( Travis Unknown )