docker rmi -f works with stopped containers + revamped error messages

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
update message

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Update hack/dind to match the rest of our scripts

No functional changes here, just coding style and maintainability.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
cli.md: Fix up Markdown formatting by adding one `
Don't restrict lxc because of apparmor

We don't have the flexibility to do extra things with lxc because it is
a black box and most fo the magic happens before we get a chance to
interact with it in dockerinit.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
deregister containers before removing driver and containerGraph references

This is required to address a race condition described in #5553,
where a container can be partially deleted -- for example, the
root filesystem but not the init filesystem -- which makes
it impossible to delete the container without re-adding the
missing filesystems manually.

This behavior has been witnessed when rebooting boxes that
are configured to remove containers on shutdown in parallel
with stopping the Docker daemon.

Docker-DCO-1.1-Signed-off-by: Gabriel Monroy <gabriel@opdemand.com> (github: gabrtv)
Month devpts before mounting subdirs

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
cli.md: Add space
cli.md: Add another sudo
Merge pull request #5565 from creack/fix_devpts

Month devpts before mounting subdirs
Remove unused daemon/sorter.go

Docker-DCO-1.1-Signed-off-by: Guillaume J. Charmes <guillaume@charmes.net> (github: creack)
Merge pull request #5462 from tianon/hack-dind-style

Update hack/dind to match the rest of our scripts
cli.md: sudo at the right place

Docker-DCO-1.1-Signed-off-by: Felix Rabe <felix@rabe.io> (github: felixrabe)
Merge pull request #5567 from creack/remove_unused_file
Merge pull request #5560 from gabrtv/deregister-containers-earlier

De-register containers before removing driver and containerGraph references
Merge pull request #5566 from felixrabe/patch-5

cli.md: Add another sudo
Merge pull request #5563 from felixrabe/patch-3

cli.md: Add space
cli.md: More typos

I've seen one other missing space that I addressed in another PR already.
I don't know whether that is a common occurrence in the docs.

About the second diff chunk, it looks like some copy-paste mistake to me.

Docker-DCO-1.1-Signed-off-by: Felix Rabe <felix@rabe.io> (github: felixrabe)
api/server: better error checking to avoid unnecessary panics

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge pull request #5537 from shykes/pr_out_api_server_better_error_checking_to_avoid_unnecessary_panics