cli integration: allow driver selection via vars

This makes it possible to choose the graphdriver and the execdriver
which is going to be used for the cli integration tests.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
cli integration: fix wait race

The wait at the end of cli integration script could end up failing if
the process had already exited. This was making it look like the tests
have failed.

This change fixes the problem.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Revert "engine: fix engine.Env.Encode() to stop auto-guessing types."

This reverts commit 76057addb255e6f14dd03c276317abc759a15a80.

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Use setjson hack again for version
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Revert "remove hack in version"

This reverts commit b2b9334f27e1a773b77241efa214af2e87439d3b.

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #5027 from unclejack/cli_integration_add_docker_options

Cli integration: add docker options & fix the wait at the end
Merge pull request #5031 from crosbymichael/revert-env

Revert env changes