add pkg/chrootarchive and use it on the daemon

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)

chrootarchive/init.go

@@ -0,0 +1,18 @@
+package chrootarchive
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/docker/docker/pkg/reexec"
+)
+
+func init() {
+	reexec.Register("docker-untar", untar)
+	reexec.Register("docker-applyLayer", applyLayer)
+}
+
+func fatal(err error) {
+	fmt.Fprint(os.Stderr, err)
+	os.Exit(1)
+}