Fix shard ID logging in DWSDIT#testAckedIndexing

This commit fixes a minor issue with the shard ID that is logged while
indexing in DiscoveryWithServiceDisruptionsIT#testAckedIndexing. The
issue is that the operation routing hash could lead to a negative
remainder modulo the number of primaries (if the hash itself is
negative) but should instead be the normalized positive remainder. This
issue only impacts the logging of the shard ID as the actual shard ID
used during indexing is computed elsewhere but would cause the shard ID
in the affected logging statement to not match shard IDs that are logged
elsewhere.

core/src/test/java/org/elasticsearch/discovery/DiscoveryWithServiceDisruptionsIT.java

@@ -45,6 +45,7 @@ import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.Priority;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.collect.Tuple;
+import org.elasticsearch.common.math.MathUtils;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.discovery.zen.ZenDiscovery;
@@ -465,7 +466,7 @@ public class DiscoveryWithServiceDisruptionsIT extends ESIntegTestCase {
                                 logger.info("[{}] Acquired semaphore and it has {} permits left", name, semaphore.availablePermits());
                                 try {
                                     id = Integer.toString(idGenerator.incrementAndGet());
-                                    int shard = Murmur3HashFunction.hash(id) % numPrimaries;
+                                    int shard = MathUtils.mod(Murmur3HashFunction.hash(id), numPrimaries);
                                     logger.trace("[{}] indexing id [{}] through node [{}] targeting shard [{}]", name, id, node, shard);
                                     IndexResponse response = client.prepareIndex("test", "type", id).setSource("{}").setTimeout("1s").get();
                                     assertThat(response.getVersion(), equalTo(1l));