Clean up the docker socket on termination of the daemon.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Merge pull request #6962 from erikh/3349-cleanup-docker-socket

Clean up the docker socket on termination of the daemon.
Add "docker create" support

This exposes the already existing "create container" operation.  It is
very similar to "docker run -d" except it doesn't actually start the
container, but just prepares it. It can then be manually started using
"docker start" at any point.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

Conflicts:
	api/client/commands.go
	runconfig/parse.go
integration-cli: Add docker create tests

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: tiborvass)
docs fix

Docker-DCO-1.1-Signed-off-by: Tibor Vass <teabee89@gmail.com> (github: tiborvass)