ZOOKEEPER-3981: Flaky test MultipleAddressTest::testGetValidAddressWithNotValid

Problem:

Test MultipleAddressTest::testGetValidAddressWithNotValid might fail deterministically when the address it's using, 10.0.0.1, is reachable, as per https://tools.ietf.org/html/rfc5735 10.0.0.1 might be allocatable to private network usage. In fact, the router address of my ISP is assigned this IP, leading to this test always failing for me.

Solution:

Replace the address with 240.0.0.0, which is reserved for future use and less likely to be reachable.

Author: Michael Han <michael@lianghan.org>
Author: Michael Han <hanm@apache.org>

Reviewers: Christopher Tubbs <ctubbsii@apache.org>, Mate Szalay-Beko <symat@apache.org>

Closes #1511 from hanm/fixut

zookeeper-server/src/test/java/org/apache/zookeeper/server/quorum/MultipleAddressesTest.java

@@ -110,7 +110,8 @@ public class MultipleAddressesTest {
     @Test
     public void testGetValidAddressWithNotValid() {
         assertThrows(NoRouteToHostException.class, () -> {
-            MultipleAddresses multipleAddresses = new MultipleAddresses(new InetSocketAddress("10.0.0.1", 22));
+            // IP chosen because it is reserved for documentation/examples and should be unreachable (RFC 5737)
+            MultipleAddresses multipleAddresses = new MultipleAddresses(new InetSocketAddress("203.0.113.1", 22));
             multipleAddresses.getReachableAddress();
         });
     }
@@ -259,4 +260,4 @@ public class MultipleAddressesTest {
                 .mapToObj(i -> "127.0.0." + i).collect(Collectors.toList());
     }
 
-}
+}