HADOOP-16126. ipc.Client.stop() may sleep too long to wait for all connections.

(cherry picked from commit 0edb0c51dc2c4ae2f353e260f01912e28033d70f)

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ipc/Client.java

@@ -86,6 +86,7 @@ import static org.apache.hadoop.ipc.RpcConstants.PING_CALL_ID;
 public class Client implements AutoCloseable {
   
   public static final Logger LOG = LoggerFactory.getLogger(Client.class);
+  private static final int STOP_SLEEP_TIME_MS = 10;
 
   /** A counter for generating call IDs. */
   private static final AtomicInteger callIdCounter = new AtomicInteger();
@@ -1336,7 +1337,7 @@ public class Client implements AutoCloseable {
     // wait until all connections are closed
     while (!connections.isEmpty()) {
       try {
-        Thread.sleep(100);
+        Thread.sleep(STOP_SLEEP_TIME_MS);
       } catch (InterruptedException e) {
       }
     }