ofctl lib: Actions is a list

Signed-off-by: Satoshi Kobayashi <satoshi-k@stratosphere.co.jp>
Acked-by: OHMURA Kei <ohmura.kei@lab.ntt.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>