[FLINK-17750][tests] Harden YARNHighavailabilityITCase by increasing …

…ZK session timeout to 20s

In order to harden YARNHighAvailabilityITCase against ZK session timeouts, the timeout has been increased
from 1s to 20s. This increase also increases the runtime of YARNHighAvailabilityITCase.testKillYarnSessionClusterEntrypoint
slightly.

This closes apache#12347.

flink-yarn-tests/src/test/java/org/apache/flink/yarn/YARNHighAvailabilityITCase.java

@@ -274,7 +274,7 @@ private YarnClusterDescriptor setupYarnClusterDescriptor() {
 		flinkConfiguration.setString(HighAvailabilityOptions.HA_MODE, "zookeeper");
 		flinkConfiguration.setString(HighAvailabilityOptions.HA_STORAGE_PATH, storageDir);
 		flinkConfiguration.setString(HighAvailabilityOptions.HA_ZOOKEEPER_QUORUM, zkServer.getConnectString());
-		flinkConfiguration.setInteger(HighAvailabilityOptions.ZOOKEEPER_SESSION_TIMEOUT, 1000);
+		flinkConfiguration.setInteger(HighAvailabilityOptions.ZOOKEEPER_SESSION_TIMEOUT, 20000);
 
 		flinkConfiguration.setString(RestartStrategyOptions.RESTART_STRATEGY, "fixed-delay");
 		flinkConfiguration.setInteger(RestartStrategyOptions.RESTART_STRATEGY_FIXED_DELAY_ATTEMPTS, Integer.MAX_VALUE);