Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  James Myers:
     Fix typo in buildpack_bits_controller ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/24046000 )
     Refactor buildpack_bits_controller to use Blob instead of file ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/24044498 )
     Make Blobstore::Client#file a public method ( Travis Unknown )

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