This patch adds SELinux labeling support.

docker will run the process(es) within the container with an SELinux label and will label
all of  the content within the container with mount label.  Any temporary file systems
created within the container need to be mounted with the same mount label.

The user can override the process label by specifying

-Z With a string of space separated options.

-Z "user=unconfined_u role=unconfined_r type=unconfined_t level=s0"

Would cause the process label to run with unconfined_u:unconfined_r:unconfined_t:s0"

By default the processes will run execute within the container as svirt_lxc_net_t.
All of the content in the container as svirt_sandbox_file_t.

The process mcs level is based of the PID of the docker process that is creating the container.

If you run the container in --priv mode, the labeling will be disabled.

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
Add vendored version of github.com/guelfey/go.dbus

We need this to do systemd API calls.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Add systemd.SdBooted()

This is a conversion of sd_booted() from libsystemd to go and checks
if the system was booted with systemd.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
systemd: Add bindings for some systemd dbus calls

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
cgroups: Add systemd implementation of cgroups

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Make execdriver a per container property

This way we can have different (non-default) exec drivers for some
containers.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Move execdriver construction into execdriver/execdrivers

This can't be in execdriver (dependency loop) but should not be
hardcoded inside runtime.go either. So we put it in a subpackage.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Add "foreground" mode for docker run

This is a mode of "docker run" that uses direct forking from the
docker client, meaning that the container is a direct child of the
docker run command (rather than the daemon), and that it directly
inherits stdout/err (and stdin if requested) from the parent of the
"docker run" command.

This is very useful in cases where you e.g. want to run a docker
container from systemd (or other process manager), as we can use the
process manager to e.g. set up cgroups and limits, monitor and
restart, pass in fds for socket activation, etc.

The way this works is that there is a new execdriver, which is used
for forground containers. This container just does rpc calls back to
the "docker run" command, which in turn uses a "real" execdriver and
feeds it whatever data the "fake" execdriver got, but in the context
of the docker run command.

We feed information about the process (exit status, pid, etc) to the
daemon, so it is visible just like any other docker container via the
docker apis.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

Conflicts:
	runconfig/parse.go
systemd: Add SetUnitProperties() wrapper

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Add -reuse-unit flag to allow reusing an existing systemd cgroup/unit

This flag, which works only if specified in combination with the
-foreground switch causes docker to not create a new transient unit
for the container, but rather reuse the current systemd unit for
resource limits.

This allows e.g. a systemd unit file to contain:
ExecStart=docker run -f -reuse-unit the-image

And docker will use the cgroup of the foo.service unit, allowing
nice integration with systemd.

Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)

Conflicts:
	runconfig/parse.go
Ignore *.patch and *~ in git

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
Remount /var/lib/docker as --private to fix scaling issue

If an admin mounts all file systems as -rshared (Default on RHEL and Fedora)
we see a scaling problem as the number of container increase.

Basically every new container needs to have it new mounts in /var/lib/docker
shared to all other containers, this ends up with us only able to scale to
around 100 containers, before the system slows down.

By simply bind mounting /var/lib/docker on its and then setting it private,
the scaling issue goes away.
Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)
Setup LISTEN_PID correctly for socket activations
Inform processes in the container that they are running in a docker container

Init systems like systemd use this to determine they are running in a non
privleged environment.