Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Phan Le:
     Finish StagingsController refactoring ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/23796492 )
     Refactor stagings_controller. ( Travis Unknown )
     Minor test refactoring ( Travis Unknown )

Signed-off-by: Kai Zhang <kaizhang@cn.ibm.com>