Fixed counter state.

Author: AlexeyKuznetsov-DD

dd-trace-core/src/main/java/datadog/trace/common/writer/ListWriter.java

@@ -137,10 +137,16 @@ public boolean flush() {
     return true;
   }
 
+  @Override
+  public void clear() {
+    super.clear();
+
+    traceCount.set(0);
+  }
+
   @Override
   public void close() {
     clear();
-    traceCount.set(0);
   }
 
   @Override