Bump grootfs
Bump grootfs

  > Update root's GOPATH in CI docker image
  > Bump golang version to 1.8.3 on CI image
  > Bump bosh-cli version to 2.0.28 on ci
  > Bump cf cli version in CI image
  > Widen acceptable window for duration metric emitter test

masters-of-cats/grootfs-release,masters-of-cats/grootfs-release