add script that lists unused blobs
Bump src/cloud_controller_ng, src/collector

Move total_users collector metric from HM to CC

Bump cloudfoundry/cloud_controller_ng:
  Phan Le and Ruth Byers:
     Delete old droplets when a new one uploaded ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12638111 )
     Show SQL statements in logs ( Travis Unknown )
     Fixed the flakey test. ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12627731 )
     Revert "Revert "Refactor StagingsController"" ( Travis Unknown )
     Only create a new droplet if the upload to blobstore succeded. ( Travis Failed: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12596731 )
     Don't unlink the log file before each test. We want to tail -f the logs. ( Travis Unknown )
     Destroy droplet on hard and soft delete of app ( Travis Unknown )
     Removed unused code ( Travis Unknown )
  phanle:
     Revert "Refactor StagingsController" ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12621258 )
     Refactor StagingsController ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12604850 )
  Phan Le:
     App can track multiple versions of the droplets. ( Travis finished: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12583969 )
     Added rspec parallel options ( Travis Unknown )
     Ignore tmp dir ( Travis Unknown )
     Renamed variable name. [Finish #57819156] ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12543214 )
     Removed the actual uploaded file (with the full path rather than just the file name) ( Travis Unknown )
     Move debugger gem to test mode ( Travis Unknown )
  Karen Wang and Phan Le:
     Renamed Droplet class to BlobstoreDroplet. ( Travis Unknown )
  Onsi Fakhouri, Phan Le and Sarah Chandler:
     add user cc_user_count to varz end point ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12548579 )
  Jeff Schnitzer and Jimmy Da:
     Use expected restcontroller exceptions during authentication. ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12547843 )
     Fix error message for service name invalid. ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12528761 )
  Alex Suraci:
     querying service tokens by label and provider ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12547685 )
     allow creation of shared domains through the API ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12544579 )
  Ian Lesperance and Nicole Sullivan:
     Include binding count in service instance summary ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/12547527 )
  Ian Lesperance and Jimmy Da:
     Reject invalid service names before attempt to provision ( Travis Unknown )
Bump cloudfoundry/collector:
  Onsi Fakhouri and Sarah Chandler:
     total_users is now provided by CC, not HM.  removed user_rate ( Travis Success: https://travis-ci.org/cloudfoundry/collector/builds/12632343 )