fix some comment

bookkeeper-server/src/main/java/org/apache/bookkeeper/client/api/BookKeeper.java

@@ -87,6 +87,7 @@ static BookKeeperBuilder newBuilder(final ClientConfiguration clientConfiguratio
      * @return the metadata service is available.
      */
     CompletableFuture<Boolean> isDriverMetadataServiceAvailable();
+
     /**
      * Close the client and release every resource.
      *

bookkeeper-server/src/main/java/org/apache/bookkeeper/meta/zk/ZKMetadataDriverBase.java

@@ -68,6 +68,7 @@ public class ZKMetadataDriverBase implements AutoCloseable {
     protected static final String SCHEME = "zk";
 
     protected volatile boolean metadataServiceAvailable;
+
     private static final int ZK_CLIENT_WAIT_FOR_SHUTDOWN_TIMEOUT_MS = 5000;
 
     public static String getZKServersFromServiceUri(URI uri) {

bookkeeper-server/src/test/java/org/apache/bookkeeper/client/api/DriverMetadataServiceAvailableTest.java

@@ -40,7 +40,6 @@ public DriverMetadataServiceAvailableTest() {
     @Test
     public void testDriverMetadataServiceAvailable()
             throws Exception {
-
         ClientConfiguration conf = new ClientConfiguration();
         conf.setMetadataServiceUri(zkUtil.getMetadataServiceUri());
         conf.setZkTimeout(3000);