As discussed in https://github.com/docker/docker/issues/16623, the API calls for setting ENV-vars lacked an actual example. This PR adds some examples to the API calls. Signed-off-by: Sebastiaan van Stijn <github@gone.nl> Upstream-commit: e41de3e6318ad4cb30eabab9bec60f9fb9d7a76b Component: engine