[SPARK-18588][TESTS] Ignore KafkaSourceStressForDontFailOnDataLossSuite

## What changes were proposed in this pull request?

Disable KafkaSourceStressForDontFailOnDataLossSuite for now.

## How was this patch tested?

Jenkins

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #16275 from zsxwing/ignore-flaky-test.

external/kafka-0-10-sql/src/test/scala/org/apache/spark/sql/kafka010/KafkaSourceSuite.scala

@@ -845,7 +845,7 @@ class KafkaSourceStressForDontFailOnDataLossSuite extends StreamTest with Shared
     }
   }
 
-  test("stress test for failOnDataLoss=false") {
+  ignore("stress test for failOnDataLoss=false") {
     val reader = spark
       .readStream
       .format("kafka")