ofp-util: Fix table features decoding of multiple tables.

Table features replies can be packed back-to-back within a single
multipart reply.  The code here didn't properly parse properties when this
occurred.  This fixes the problem.

There is no test in the current tree that exercises this decoding, but an
upcoming commit that adds ofproto support for table-features requests will
add one.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>