Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

e2e test: use sleep to wait in hostexec

**What this PR does / why we need it**:

The test image hostexec waits forever by reading a named pipe that nobody writes.
https://github.com/kubernetes/kubernetes/blob/09cf6c9776572fcf73a7cfdf45df9a8a315e17ba/test/images/hostexec/Dockerfile#L25

Because of https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=c6c70f4455d1eda91065e93cc4f7eddf4499b105, on OS images with kernel 4.11+, the wait will be interrupted unexpectedly.

```
ygg@ubuntu-gke-1604-xenial-v20171222-vm:~$ sudo docker run -d gcr.io/kubernetes-e2e-test-images/hostexec-amd64:1.0
a428c06ebd3b9a13504e453107d3fb69e859f731cae3ca0fdf898a646e394632
ygg@ubuntu-gke-1604-xenial-v20171222-vm:~$ sudo docker exec -it a428c06ebd /bin/sh
/ # timeout -t 1 cat
Terminated
ygg@ubuntu-gke-1604-xenial-v20171222-vm:~$ sudo docker logs a428c06ebd        
/bin/sh: can't open /fifo: Interrupted system call
```

Changed to use `sleep` to avoid this issue.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:

This PR fixes the test failure in https://k8s-gubernator.appspot.com/build/kubernetes-jenkins/logs/ci-kubernetes-e2e-gke-ubuntustable1-k8sstable1-reboot/3140

**Special notes for your reviewer**:

**Release note**:

```
None
```