Bump src/cloud_controller_ng

Bump cloudfoundry/cloud_controller_ng:
  Chris Adams:
     Merge pull request #233 from sykesm/diego-staged-event ( Travis started: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/25019334 )
  Derek Richard:
     Add /v2/apps/:guid/env and bump CC version ( Travis Success: https://travis-ci.org/cloudfoundry/cloud_controller_ng/builds/24997737 )
  Matthew Sykes:
     Update detected buildpack on diego staging path ( Travis Unknown )

Signed-off-by: Sabha Parameswaran <sparameswaran@gopivotal.com>
Change default bosh-lite stemcell to go-agent
Merge remote-tracking branch 'upstream/develop' into develop