Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Ruth Byers:
     Nginx waits for requests to complete before shutting down ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/21791575 )

* Adds drain script for Nginx

Signed-off-by: Ruth Byers <rbyers@pivotallabs.com>