add pkg/chrootarchive and use it on the daemon

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

Conflicts:
	builder/internals.go
	daemon/graphdriver/aufs/aufs.go
	daemon/volumes.go
		fixed conflicts in imports

reexec/command_linux.go

@@ -0,0 +1,18 @@
+// +build linux
+
+package reexec
+
+import (
+	"os/exec"
+	"syscall"
+)
+
+func Command(args ...string) *exec.Cmd {
+	return &exec.Cmd{
+		Path: Self(),
+		Args: args,
+		SysProcAttr: &syscall.SysProcAttr{
+			Pdeathsig: syscall.SIGTERM,
+		},
+	}
+}