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)
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)
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)
Remove trailing slash from host parameter in docker init.

(This causes errors on Docker 0.8)

Docker-DCO-1.1-Signed-off-by: Morgante Pell <morgante.pell@morgante.net> (github: morgante)
registry: Added simple checksums (sha256) for layers

Docker-DCO-1.1-Signed-off-by: Sam Alba <sam@docker.com> (github: samalba)
registry: Fixed tests

Docker-DCO-1.1-Signed-off-by: Sam Alba <sam@docker.com> (github: samalba)
seperate out the terminal functions from lxc to the pkg/term

  Since these functions are indepenent of lxc, and could be used by
  other drivers.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
api/common.go: code shared by the server and client implementation of the Docker remote api.

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Move the terminal setup to execdriver, instead of ./pkg/term

  It is independent of any particular driver, but likely used by
  multiple execdrivers. Also, pkg/... is not to have any links to
  docker, which this terminal setup does.

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)
Engine: cleanup side effects between tests

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Engine: builtin command 'commands' returns a list of registered commands

Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Adjust kernel version parsing to be more lenient of strange things like "3.12-1-amd64"

Docker-DCO-1.1-Signed-off-by: Andrew Page <admwiggin@gmail.com> (github: tianon)
registry: Removed checksumPayload from exported fields

Docker-DCO-1.1-Signed-off-by: Sam Alba <sam@docker.com> (github: samalba)
Use the cpu cgroup subsystem instead of memory because its non optional
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)
fix gofmt

Docker-DCO-1.1-Signed-off-by: Victor Vieux <victor.vieux@docker.com> (github: vieux)
Merge pull request #4313 from shykes/api-common

api/common.go
Merge pull request #4309 from crosbymichael/change-cgroup-subsystem

Use the cpu cgroup subsystem instead of memory because its non optional
Merge pull request #4296 from morgante/patch-1

Remove trailing slash from --host parameter in contrib/vagrant-docker/README.md
Merge pull request #4189 from vbatts/vbatts-execdriver_flag

execdriver flag for docker daemon
fix divide by zero error

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