Set longer settings update task timeout

It appears that task cancelation is executed before the settings update is
event starting in testClusterSettingsUpdateNotAcknowledged. This change uses
longer timeout to improve the probability of blocking.

server/src/internalClusterTest/java/org/elasticsearch/cluster/settings/ClusterSettingsUpdateWithFaultyMasterIT.java

@@ -62,7 +62,7 @@ public void testClusterSettingsUpdateNotAcknowledged() throws Exception {
             .cluster()
             .prepareUpdateSettings()
             .setPersistentSettings(Settings.builder().put(BlockingClusterSettingTestPlugin.TEST_BLOCKING_SETTING.getKey(), true).build())
-            .setMasterNodeTimeout(TimeValue.timeValueMillis(10L))
+            .setMasterNodeTimeout(TimeValue.timeValueMillis(100L))
             .execute();
 
         logger.info("--> waiting for cluster state update to be blocked");