Bump Elasticsearch6 version to 6.8.12

Author: zhangmeng56

flink-connectors/flink-connector-elasticsearch6/src/test/java/org/apache/flink/streaming/connectors/elasticsearch/table/Elasticsearch6DynamicSinkITCase.java

@@ -66,7 +66,7 @@ public class Elasticsearch6DynamicSinkITCase {
     public static ElasticsearchContainer elasticsearchContainer =
             new ElasticsearchContainer(
                     DockerImageName.parse("docker.elastic.co/elasticsearch/elasticsearch-oss")
-                            .withTag("6.3.1"));
+                            .withTag("6.8.12"));
 
     @SuppressWarnings("deprecation")
     protected final Client getClient() {

flink-connectors/flink-connector-elasticsearch6/src/test/java/org/apache/flink/streaming/connectors/elasticsearch6/ElasticsearchSinkITCase.java

@@ -45,7 +45,7 @@ public class ElasticsearchSinkITCase
     public static ElasticsearchContainer elasticsearchContainer =
             new ElasticsearchContainer(
                     DockerImageName.parse("docker.elastic.co/elasticsearch/elasticsearch-oss")
-                            .withTag("6.3.1"));
+                            .withTag("6.8.12"));
 
     @Override
     protected String getClusterName() {

flink-end-to-end-tests/run-nightly-tests.sh

@@ -206,7 +206,7 @@ fi
 run_test "Netty shuffle direct memory consumption end-to-end test" "$END_TO_END_DIR/test-scripts/test_netty_shuffle_memory_control.sh"
 
 run_test "Elasticsearch (v5.3.3) sink end-to-end test" "$END_TO_END_DIR/test-scripts/test_streaming_elasticsearch.sh 5 https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-5.3.3.tar.gz"
-run_test "Elasticsearch (v6.3.1) sink end-to-end test" "$END_TO_END_DIR/test-scripts/test_streaming_elasticsearch.sh 6 https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.3.1.tar.gz"
+run_test "Elasticsearch (v6.8.12) sink end-to-end test" "$END_TO_END_DIR/test-scripts/test_streaming_elasticsearch.sh 6 https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.8.12.tar.gz"
 
 run_test "Quickstarts Java nightly end-to-end test" "$END_TO_END_DIR/test-scripts/test_quickstarts.sh java"
 run_test "Quickstarts Scala nightly end-to-end test" "$END_TO_END_DIR/test-scripts/test_quickstarts.sh scala"