Update hack/dind to mount cgroups on "/cgroup" instead of "/sys/fs/cgroup" for better compatibility

Fixes #5122

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Introduce x-axe scrolling to code-blocks.

This improvement introduces x-axe scrolling to code-blocks by
overriding certain default bootstrap word-wrapping constraints.

This PR closes: https://github.com/dotcloud/docker/issues/5279

Docker-DCO-1.1-Signed-off-by: O.S. Tezer <ostezer@gmail.com> (github: ostezer)
registry: adding vbatts to the MAINTAINERS

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Cast Input and Output to closer
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Rewrite and update the MongoDB service article

MongoDB article had some fundemental issues.

 - Outdated Dockerfile
 - Insufficient / unclear instructions
 - Unnecessary comments
 - Failed to explain the role of Docker.io
 - Did not have a complete Dockerfile sample
 - Lacked a "learn more" section / link to Trusted Builds

This update aims to address all these issues with a complete re-write.

It also:

 - Corrects the label under which this article is/was listed on the menu

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

 - First run at amending after the initial review process.
 - Make the Dockerfile generic.
 - Revision.
 - Fixes
Merge pull request #5599 from ostezer/docs-rewrite-examples-mongodb

Rewrite and update the MongoDB service article
Merge pull request #5583 from ostezer/docs-ui-add-codeblock-scrolling

Introduce x-axe scrolling to code-blocks.
Added value format description for VOLUME instruction

In the documentation was not mentioned explicitly that VOLUME value
shoud be a valid JSON array. Because of this I spent time to discovering
the problem with my image where I put `VOLUME ['/data']` (with single quotes).
The `['/data']` mount point was parsed and mounted whole as a string without
any errors and warnings.

Docker-DCO-1.1-Signed-off-by: Max Shytikov <mshytikov@gmail.com> (github: mshytikov)
Merge pull request #5697 from mshytikov/fix/doc

Added value format description for VOLUME instruction in builder doc
Merge pull request #5686 from crosbymichael/cast-to-closer

Cast Input and Output to io.Closer
Merge pull request #5463 from tianon/hack-dind-cgroup

Update hack/dind to mount cgroups on "/cgroup" instead of "/sys/fs/cgroup" for better compatibility
returns an error when using -h and --net

Docker-DCO-1.1-Signed-off-by: Victor Vieux <vieux@docker.com> (github: vieux)
Merge pull request #5709 from vieux/conflict_h_net

returns an error when using -h and --net
Fix stdin handling in engine.Sender and engine.Receiver

This introduces a superficial change to the Beam API:

* `beam.SendPipe` is renamed to the more accurate `beam.SendRPipe`
* `beam.SendWPipe` is introduced as a mirror to `SendRPipe`

There is no other change in the beam API.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: fix a timeout bug in Sender/Receiver

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: slightly more stress-testing of Receiver/Sender to reproduce the hang problem

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Merge pull request #5687 from shykes/pr_out_engine_fix_a_timeout_bug_in_sender_receiver
Engine: ensure all pipes are properly closed by Receiver and Sender

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)

[michael@docker.com: fix stdin closing in engine.Job.Run]
[michael@docker.com: fix fd leak in engine.Receiver.Run]
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)

Docker-Tested-By: Solomon Hykes <solomon@docker.com>
Docker-Tested-by: Michael Crosby <michael@docker.com>
Merge pull request #5713 from shykes/pr_out_engine_ensure_all_pipes_are_properly_closed_by_receiver_and_sender
beam/data: Message.GetOne() returns the last value set at a key

This is a convenience for callers which are only interested in one value
per key. Similar to how HTTP headers allow multiple keys per value, but
are often used to store and retrieve only one value.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)