of1.3: fix OFPMeterStats

len -> length
as the latter seems to be expected by OFPMultipartReply.parser_stats_body.

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of1.3: fix OFP_GROUP_DESC_STATS_PACK_STR

Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
of1.2: OFPGroupFeaturesStats: tuple -> list

tuples are json-unfriendly.

(of1.3 version was completely broken until very recently
and the way i fixed it is consistent with this change.)

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