Ts 3140: fix crash problem between the delay of releasing ProtocolProbeTrampoline and setting spdy continuation

when ProtocolProbeTrampoline is finished to probe the next protocol to use, it will be deleted and then next protocol handler will be set at 'probeParent->endpoint[key]->accept', but for spdy, the function of setting the correct continuation to UnixNetVConnection::do_io_read is put into the thread event queue. This is a chance that check_inactivity timeout event occurs before the former spdy set event, in this case, crash will happen.