Update contrib/check-config.sh to check for CGROUP_FREEZER (which is newly required), and to use /proc/mounts for checking if we have a cgroup hierarchy instead of using /proc/$$/mountinfo (which on systemd might not list the cgroup hierarchy)

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
registry: remove unneeded time.Duration()

These constants don't need to use time.Duration(). Fixup this file since
it seems to be the only one using this style.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Avoid history expansion.

Docker-DCO-1.1-Signed-off-by: Jeff Welch <whatthejeff@gmail.com> (github: whatthejeff)
Improve documentation on Ubuntu for getting the latest release of
docker.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)
Repaired broken links
Docker-DCO-1.1-Signed-off-by: Calin Cruceru <crucerucalincristian@gmail.com> (github: crucerucalin)
Fixed up if statement

Signed-off-by: Levi Gross <levi@levigross.com>

Docker-DCO-1.1-Signed-off-by: Levi Gross <levi@levigross.com> (github: levigross)
Merge pull request #6252 from tianon/update-check-config

Update contrib/check-config.sh to check for CGROUP_FREEZER and to use /proc/mounts
Merge pull request #6300 from whatthejeff/patch-1

Avoid history expansion.
Merge pull request #6315 from erikh/ubuntu-latest-install-docs

Improve documentation on Ubuntu for getting the latest release of docker.
Merge pull request #6322 from crucerucalin/master

Repaired broken links in docs/sources/faq.md
docs: Fix docs' styling conflict with common names

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)

Closes issue #6329
Merge pull request #6339 from ostezer/docs-fix-css-title-conflict

docs: Fix docs' styling conflict with common names
Remove and vendor libcontainer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Update libcontainer imports
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Use libcontainer version tag for vendor script
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix some bullet points so they render correctly.
minor spelling fix
Merge pull request #6349 from chrismckinnel/master

Fix some bullet points so they render correctly.
Merge pull request #6351 from lenw/patch-1

minor spelling fix
Merge pull request #6277 from philips/remove-unneeded-time-duration

registry: remove unneeded time.Duration()