Bump docker-circus

[#78292566]

Bump cloudfoundry-incubator/docker-circus:
  Abhijit Hiremagalur:
     Remove Godeps; deps are vendored in diego-release ( Travis created: https://travis-ci.org/cloudfoundry-incubator/docker-circus/builds/35478752 )
  Peter Parente:
     Support Cmd and Entrypoint in docker soldier ( Travis Unknown )

Signed-off-by: Matthew Sykes <matthew.sykes@gmail.com>