Automatic merge from submit-queue (batch tested with PRs 50670, 50332)

e2e test for local storage mount point

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

We discovered that kubernetes can treat local directories and actual mountpoints differently. For example, https://github.com/kubernetes/kubernetes/issues/48331. The current local storage e2e tests use directories.

This PR introduces a test that creates a tmpfs and mounts it, and runs one of the local storage e2e tests.

**Which issue this PR fixes**: fixes https://github.com/kubernetes/kubernetes/issues/49126

**Special notes for your reviewer**:

I cherrypicked PR https://github.com/kubernetes/kubernetes/pull/50177, since local storage e2e tests are broken in master on 2017-08-08 due to "no such host" error. This PR replaces NodeExec with SSH commands.

You can run the tests using the following commands:
``` 
$ NUM_NODES=1 KUBE_FEATURE_GATES="PersistentLocalVolumes=true" go run hack/e2e.go -- -v --up
$ go run hack/e2e.go -- -v --test --test_args="--ginkgo.focus=\[Feature:LocalPersistentVolumes\]"
```

Here are the summary of results from my test run:
```
Ran 9 of 651 Specs in 387.905 seconds
SUCCESS! -- 9 Passed | 0 Failed | 0 Pending | 642 Skipped PASS

Ginkgo ran 1 suite in 6m29.369318483s
Test Suite Passed
2017/08/08 11:54:01 util.go:133: Step './hack/ginkgo-e2e.sh --ginkgo.focus=\[Feature:LocalPersistentVolumes\]' finished in 6m32.077462612s
```

**Release note**:
`NONE`