Automatic merge from submit-queue

Interrupt/Terminate all child processes on timeout. Auto-gen stepName

Signal all children of the finishRunning command. See http://stackoverflow.com/questions/22470193/why-wont-go-kill-a-child-process-correctly

Most commands started by e2e.go are shell scripts like `hack/ginkgo-e2e.sh`, `hack/e2e-internal/e2e-down.sh`, etc which quickly starts a subprocess such as the ginkgo binary. We spend ~1s in ginkgo-e2e.sh and hours inside the ginkgo binary. Therefore when we want to timeout it is important that we signal the child processes as well, which we can accomplish by starting the command in a new process group, and signaling `-pid` instead of `pid`

Ref https://github.com/kubernetes/test-infra/issues/1316 https://github.com/kubernetes/test-infra/issues/1250
Test results: https://github.com/kubernetes/kubernetes/pull/37868