initial version of cli integration tests

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Small tweaks to the hack scripts to make them simpler

Please do with this as you please (including rebasing and/or squashing it), especially under clause (c) of the DCO.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Reduce error level form harmless errors

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
Merge pull request #4922 from creack/reduce_error_lvl

Reduce error level form harmless errors
Merge pull request #4505 from unclejack/cli_integration_tests

cli integration tests