ofctl_v1_0/2/3: check lock timeout by lock.is_set().

send_stats_request never catches hub.Timeout exception because it
has been caught by the event wait function itself.

Signed-off-by: Wei-Li Tang <alextwl@xinguard.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>