Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  James Myers and Matt Hess:
     Revert "Avoid time zone and DST-related bugs by switching to Time.current." ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/40015178 )
  Johannes Petzold:
     refactor app observer specs [#76898498] ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/40007146 )
  Amit Gupta:
     Operator switching CC Diego flags correctly switches behaviour of apps ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/39995369 )