registry: make certain headers optional

For a pull-only, static registry, there only a couple of headers that
need to be optional (that are presently required.
* X-Docker-Registry-Version
* X-Docker-Size
* X-Docker-Endpoints

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
registry: Info collection

roll version and standalone information into the _ping. And to support
Headers they are checked after the JSON is loaded (if there is anything
to load). To stay backwards compatible, if the _ping contents are not
able to unmarshal to RegistryInfo, do not stop, but continue with the
same behavior.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Engine: optional Logging field to disable custom logging in engine.

* The default behavior is preserved
* This disables the use of the `TEST` environment variable in engine.

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

The current load script does alot of things.  If it does not find the
parser loaded on the system it will just exit 0 and not load the
profile.  We think it should fail loudly if it cannot load the profile
and apparmor is enabled on the system.
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move apparmor to top level pkg
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Ignore is not exist error
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Ignore not exist errors for joining default subsystems
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Generate imports based on what is avaliable
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move network settings into separate file
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Refactor container start to make it more manageable
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Remove container.When method
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix resolvconf logic
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Remove ArgsAsString because its a util function
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Fix unmount when host volume is removed

Fixes #5244
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Merge pull request #5211 from crosbymichael/update-cgroup-defaults

Ignore not exist errors for joining default subsystems
Adding myself to the MAINTAINERS file.

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

Docker-DCO-1.1-Signed-off-by: Dan McPherson <dmcphers@redhat.com> (github: danmcp)
move the documentation to markdown

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: )
Merge pull request #5206 from SvenDowideit/stage-markdown

move the documentation to markdown
move the documentation to markdown

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)