bump atc
bump atc

[finishes #117402151]

Submodule src/github.com/concourse/atc b244bd4..599699d:
  > remove unnecessary channels from runScript
  > signal resource process instead of container.Stop

Signed-off-by: Kris Hicks <6d3f751023bc04266d4da2ff94804f4240839fe2@pivotal.io>

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