Update exec.go to latest from k8s 1.3.0
Update exec.go to latest from k8s 1.3.0

soiff/gitlab-ci-multi-runner,ayufan/gitlab-ci-multi-runner,soiff/gitlab-ci-multi-runner,hu19891110/gitlab-ci-multi-runner,hu19891110/gitlab-ci-multi-runner,soiff/gitlab-ci-multi-runner,hu19891110/gitlab-ci-multi-runner,ayufan/gitlab-ci-multi-runner,ayufan/gitlab-ci-multi-runner