Move all bind-mounts in the container inside the namespace

This moves the bind mounts like /.dockerinit, /etc/hostname, volumes,
etc into the container namespace, by setting them up using lxc.

This is useful to avoid littering the global namespace with a lot of
mounts that are internal to each container and are not generally
needed on the outside. In particular, it seems that having a lot of
mounts is problematic wrt scaling to a lot of containers on systems
where the root filesystem is mounted --rshared.

Note that the "private" option is only supported by the native driver, as
lxc doesn't support setting this. This is not a huge problem, but it does
mean that some mounts are unnecessarily shared inside the container if you're
using the lxc driver.

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

runtime/runtime.go

@@ -733,7 +733,7 @@ func NewRuntimeFromDirectory(config *daemonconfig.Config, eng *engine.Engine) (*
 	}
 
 	sysInfo := sysinfo.New(false)
-	ed, err := execdrivers.NewDriver(config.ExecDriver, config.Root, sysInfo)
+	ed, err := execdrivers.NewDriver(config.ExecDriver, config.Root, sysInitPath, sysInfo)
 	if err != nil {
 		return nil, err
 	}