Add LXC built in support deprecation notice

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>
(cherry picked from commit 06f6c0c7e5)

daemon/execdriver/execdrivers/execdrivers_linux.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"path"
 
+	"github.com/Sirupsen/logrus"
 	"github.com/docker/docker/daemon/execdriver"
 	"github.com/docker/docker/daemon/execdriver/lxc"
 	"github.com/docker/docker/daemon/execdriver/native"
@@ -18,6 +19,7 @@ func NewDriver(name string, options []string, root, libPath, initPath string, sy
 		// we want to give the lxc driver the full docker root because it needs
 		// to access and write config and template files in /var/lib/docker/containers/*
 		// to be backwards compatible
+		logrus.Warn("LXC built-in support is deprecated.")
 		return lxc.NewDriver(root, libPath, initPath, sysInfo.AppArmor)
 	case "native":
 		return native.NewDriver(path.Join(root, "execdriver", "native"), initPath, options)