支持span event

Author: yuqian.wjm

tracer-core/src/main/java/com/alipay/common/tracer/core/span/SofaTracerSpan.java

@@ -220,7 +220,7 @@ public void addEvent(SpanEventData eventData) {
 
     private void reportEvent() {
         SpanEventData spanEventData = events.poll();
-        while (spanEventData != null) {
+        while (spanEventData != null && eventNum.decrementAndGet() >= 0) {
             this.eventData = spanEventData;
             this.sofaTracer.reportEvent(this);
             spanEventData = events.poll();