Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Max Brunsfeld:
     In app observer spec, dont stub App#needs_staging? ( Travis created: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/31865161 )

Signed-off-by: Simon Leung <leungs@us.ibm.com>