Avoid infinite loop in HTTP/2 distributor toString()

Motivation:

Although effectively unused, the toString() of
WeightedFairQueueByteDistributor.State is useful for debugging. It
accidentally had an infinite loop, as it would recurse infinitely
between a parent and its child, which makes it less useful for
debugging.

Modifications:

Prune the infinite loop by using the parent's streamId instead of the
parent's toString().

Result:

Faster, less stack-overflowing toString()

codec-http2/src/main/java/io/netty/handler/codec/http2/WeightedFairQueueByteDistributor.java

@@ -770,7 +770,7 @@ public final class WeightedFairQueueByteDistributor implements StreamByteDistrib
                     .append(" flags ").append(flags)
                     .append(" pseudoTimeQueue.size() ").append(pseudoTimeQueue.size())
                     .append(" stateOnlyQueueIndex ").append(stateOnlyQueueIndex)
-                    .append(" parent ").append(parent).append("} [");
+                    .append(" parent.streamId ").append(parent == null ? -1 : parent.streamId).append("} [");
 
             if (!pseudoTimeQueue.isEmpty()) {
                 for (State s : pseudoTimeQueue) {