execdriver flag for docker daemon

  like the storage-driver flag, this implements a flag for choosing the
  execdriver to be used, defaulting to lxc.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
don't skip cert check for an example & use HTTPS

This changes two URLs from http to https and it fixes a Dockerfile to
stop skipping certificate validation. It also adds the ca-certificates
package to that Dockerfile example.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
forbid chained onbuild, from & maintainer triggers

This changes the way onbuild works:
- forbids the chaining of onbuild instructions
- forbids the use of `onbuild from`
- forbids the use of `onbuild maintainer`

It also makes docker throw errors when encountering such triggers when
executing the triggers during `FROM`.

Three tests have been added:
- ensure that chained onbuild (`onbuild onbuild`) is forbidden
- ensure that `onbuild from` is forbidden
- ensure that `onbuild maintainer` is forbidden

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Fix build command auth by adding the auth config and registry objects to the build job environment.

Docker-DCO-1.1-Signed-off-by: Jake Moshenko <jake@devtable.com> (github: jakedt)
Add newlines to the JSON stream functions

This makes the JSON streams a _lot_ easier to parse in less well-baked JSON parsers, and no less so in better ones.

Line-based JSON streams are very, very common, where simply chunk-based is not very common at all.

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
small update to API docs to go with #4276

Docker-DCO-1.1-Signed-off-by: Sven Dowideit <SvenDowideit@home.org.au> (github: SvenDowideit)
Add MTU to lxc conf to make host and container MTU match

If you are using jumbo frames the host side of the veth was being set to
1500.  Docker would set the MTU of the container side of the veth to 9001.
This would lead to a situation in which the two sides of the veth had
different MTU sizes causing issues in network traffic.

Docker-DCO-1.1-Signed-off-by: Darren Shepherd <darren.s.shepherd@gmail.com> (github: ibuildthecloud)
Merge pull request #4248 from unclejack/https_fixes

don't skip cert check for an example & use HTTPS
Fix cli argument usage typo for docker --mtu

Docker-DCO-1.1-Signed-off-by: Danny Berger <dpb587@gmail.com> (github: dpb587)
Merge pull request #4260 from unclejack/onbuild_fixes

forbid chained onbuild, from & maintainer triggers
Merge pull request #4271 from DevTable/fixbuildauth

Fix build auth by adding config to the build job environment
docs: document some JSON parameters /containers/create and /containers/(id)/start in remote api (fixes #2948)

Docker-DCO-1.1-Signed-off-by: Manuel Woelker <github@manuel.woelker.org> (github: manuel-woelker)
Add simple "grep" to hide the harmless "warning: no packages being tested depend on ..." in "go test -coverpkg ..." output

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
Merge pull request #4283 from tianon/hide-no-packages-being-tested

Add simple "grep" to hide the harmless "warning: no packages being tested depend on ..." in "go test -coverpkg ..." output
Drop -mtu from docs in favor of --mtu only

Docker-DCO-1.1-Signed-off-by: Danny Berger <dpb587@gmail.com> (github: dpb587)
Merge pull request #4277 from SvenDowideit/tianon-made-me-doit

small update to API docs to go with #4276
Merge pull request #4280 from dpb587/bugfix-mtu-typo

Fix argument usage typo for docker --mtu
Move console into execdriver
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Change Console to Terminal

Move creation and attach to driver
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
Move term creation into driver
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)