test: fix flaky test in comsumerTest (#5846)

Co-authored-by: NCai, Zhouxiang <zc31@illinois.edu>
Co-authored-by: NZhenxu Ke <kezhenxu94@apache.org>

apm-commons/apm-datacarrier/src/test/java/org/apache/skywalking/apm/commons/datacarrier/consumer/ConsumerTest.java

@@ -35,6 +35,7 @@ public class ConsumerTest {
 
     @Test
     public void testConsumerLessThanChannel() throws IllegalAccessException {
+
         final DataCarrier<SampleData> carrier = new DataCarrier<SampleData>(2, 100);
 
         for (int i = 0; i < 100; i++) {
@@ -56,6 +57,7 @@ public class ConsumerTest {
 
     @Test
     public void testConsumerMoreThanChannel() throws IllegalAccessException, InterruptedException {
+        BUFFER.drainTo(new ArrayList<SampleData>());
         final DataCarrier<SampleData> carrier = new DataCarrier<SampleData>(2, 100);
 
         for (int i = 0; i < 200; i++) {