evnsq Client::IsReady() implement wrong

[zieckey]

We must iterate every NSQConn in conns_ to check whether it is OK.

bool Client::IsReady() const {
    if (conns_.empty()) {
        return false;
    }

    return conns_[0]->IsReady();
}

And in Client::OnConnection, when the NSQConn is at 'kConnected' status, should't we move it to conns_??