Automatic merge from submit-queue

Kubelet: Start using the official docker engine-api

For #23563.

This is the **first step** in the roadmap of switching to docker [engine-api](https://github.com/docker/engine-api).
In this PR, I keep the old `DockerInterface` and implement it with the new engine-api.
With this approach, we could switch to engine-api with minimum change, so that we could:
* Test the engine-api without huge refactoring.
* Send following PRs to refactor functions in `DockerInterface` separately so as to avoid a huge change in one PR.

I've tested this PR locally, it passed all the node conformance test:
```
make test_e2e_node

Ran 19 of 19 Specs in 823.395 seconds
SUCCESS! -- 19 Passed | 0 Failed | 0 Pending | 0 Skipped PASS

Ginkgo ran 1 suite in 13m49.429979585s
Test Suite Passed
```
And it also passed the jenkins gce e2e test:
```
go run hack/e2e.go -test -v --test_args="--ginkgo.skip=\[Slow\]|\[Serial\]|\[Disruptive\]|\[Flaky\]|\[Feature:.+\]"

Ran 161 of 268 Specs in 4570.214 seconds
SUCCESS! -- 161 Passed | 0 Failed | 0 Pending | 107 Skipped PASS

Ginkgo ran 1 suite in 1h16m16.325934558s
Test Suite Passed
2016/03/25 15:12:42 e2e.go:196: Step 'Ginkgo tests' finished in 1h16m18.918754301s
```

I'm writing the design document, and will post the switching roadmap in an umbrella issue soon.

@kubernetes/sig-node