Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Ruth Byers and Raina Masand:
     Update service plan for a single existing service instance ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/38633361 )
  Chris Piraino and Luan Santos:
     Add /v2/apps/:guid/copy_bits endpoint. ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/38558531 )

Signed-off-by: Raina Masand <rmasand@pivotal.io>