Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Phan Le:
     Make cutoff_age_in_days for AppEvent and AppUsageEvent configurable ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15942797 )
     Turn Clock into a class so its easier to inject dependencies ( Travis Unknown )
     Reorganize specs by job ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15940227 )
     Make AppUsageEventsCleanup and AppEventsCleanup consistent ( Travis Unknown )
     Schedule to clean up old app events. ( Travis Unknown )
     Introduce AppEventsCleanup to cleanup old events ( Travis Failed: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15939300 )
  Eric Malm:
     Inject prune threshold into AppUsageEventCleanup job ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15939696 )
     Delete app usage events older than 31 days ( Travis Unknown )
     Introduce AppUsageEventsCleanup and enqueue to run once a day ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15912827 )
  Dave Liebreich:
     Update nokogiri to latest ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15913231 )
     Update rake gem ( Travis Unknown )
     Update :test gem group ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/15912641 )

[Finishes #62823112] [Finishes #62482050]

Signed-off-by: Phan Le <ple@pivotallabs.com>