Automatic merge from submit-queue (batch tested with PRs 63792, 63495, 63742, 63332, 63779). 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>.
add timeout for exec interface
This should get us away from situations like https://github.com/kubernetes/kubernetes/issues/63331.
A little bit more context, the `os/exec` package starts to accept `context.Context` in golang 1.7. We should leverage that so we can have a more predictable behavior, then.
```release-note
NONE
```
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