bump go-concourse
bump go-concourse

Submodule src/github.com/concourse/go-concourse c6dccd2..9be56f8:
  > update to use new container struct fields
  > add missing err check

Signed-off-by: Corbin Halliwill <38cf05332854d0c00b392ad9da3fb5cec295aa83@pivotal.io>
Signed-off-by: Robert Neumann <0e50484e9096968d17f79de0206b195d065c4510@pivotal.io>

zachgersh/concourse,concourse/concourse,zachgersh/concourse,zachgersh/concourse,concourse/concourse,concourse/concourse,cjcjameson/concourse,cjcjameson/concourse,concourse/concourse,concourse/concourse,cjcjameson/concourse