Make native driver use Exec func with different CreateCommand

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

pkg/libcontainer/nsinit/unsupported.go

@@ -7,6 +7,10 @@ import (
 	"github.com/dotcloud/docker/pkg/libcontainer"
 )
 
+func Exec(container *libcontainer.Container, term Terminal, rootfs, dataPath string, args []string, createCommand CreateCommand, startCallback func()) (int, error) {
+	return -1, libcontainer.ErrUnsupported
+}
+
 func Init(container *libcontainer.Container, uncleanRootfs, consolePath string, syncPipe *SyncPipe, args []string) error {
 	return libcontainer.ErrUnsupported
 }