Pause/freeze containers during commit

Initiates a pause before committing a container,
adds a pause option to the commit command, defaulting to 'true'.

Fixes bug: #6267

Docker-DCO-1.1-Signed-off-by: Eric Windisch <ewindisch@docker.com> (github: ewindisch)

Docker-DCO-1.1-Signed-off-by: Eric Windisch <ewindisch@docker.com> (github: )