Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Ian Lesperance and Jimmy Da:
     Raise error when unbind fails on broker ( Travis finished: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/11444298 )
  Matthew McNew:
     Updated gem dependencies to use proper timestamps in loggregator messages ( Travis finished: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/11440929 )
  Phan Le, Ruth Byers and Sarah Chandler:
     Move the logic of generating download URIs to blob store object. ( Travis finished: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/11437471 )
  Phan Le and Ruth Byers:
     use separate build pack cache blobstore in staging be able to use subdirectory of a bucket in blobstore add ability to find file and copy a public file to blobstore ( Travis Unknown )
     deleting empty file ( Travis Unknown )