KAFKA-2089; Increase metadata wait time in unit test

Increase timeout in test to avoid transient failures due to long GC or slow machine.

Author: Rajini Sivaram <rajinisivaram@googlemail.com>

Reviewers: Jun Rao <junrao@gmail.com>

Closes #2057 from rajinisivaram/KAFKA-2089

clients/src/test/java/org/apache/kafka/clients/MetadataTest.java

@@ -59,8 +59,8 @@ public class MetadataTest {
         time += refreshBackoffMs;
         assertTrue("Update needed now that backoff time expired", metadata.timeToNextUpdate(time) == 0);
         String topic = "my-topic";
-        Thread t1 = asyncFetch(topic);
-        Thread t2 = asyncFetch(topic);
+        Thread t1 = asyncFetch(topic, 500);
+        Thread t2 = asyncFetch(topic, 500);
         assertTrue("Awaiting update", t1.isAlive());
         assertTrue("Awaiting update", t2.isAlive());
         // Perform metadata update when an update is requested on the async fetch thread
@@ -307,12 +307,12 @@ public class MetadataTest {
         assertTrue("Unused topic expired when expiry disabled", metadata.containsTopic("topic4"));
     }
 
-    private Thread asyncFetch(final String topic) {
+    private Thread asyncFetch(final String topic, final long maxWaitMs) {
         Thread thread = new Thread() {
             public void run() {
                 while (metadata.fetch().partitionsForTopic(topic) == null) {
                     try {
-                        metadata.awaitUpdate(metadata.requestUpdate(), refreshBackoffMs);
+                        metadata.awaitUpdate(metadata.requestUpdate(), maxWaitMs);
                     } catch (Exception e) {
                         backgroundError.set(e.toString());
                     }