Fix QueueSubscription according to rule 3.6 & 3.9

3.6: After the Subscription is cancelled, additional Subscription.request(long n) MUST be NOPs
3.9: While the Subscription is not cancelled, Subscription.request(long n) MUST throw a java.lang.IllegalArgumentException if the argument is <= 0. The cause message MUST include a reference to this rule and/or quote the full rule