simple_switch_13: Update a comment about OVS bug

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
simple_switch_14: Update a comment about OVS bug

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
stplib.py: Should wildcard non-relevant bits in the mask field of port mod message for OpenFlow 1.2+.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>