bump atc
bump atc

[finishes #111113060]

Submodule src/github.com/concourse/atc 316edc7..2418e1e:
  > compute path once
  > make task directories deterministic

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