Pulsar standalone does not read zk port form conf/standalone.conf (ap…

…ache#3790)

### Motivation
Fixes apache#3788

### Modifications
Add codes make it read zk port from standalone.conf. And it follow the Priority: args > conf > default

pulsar-broker/src/main/java/org/apache/pulsar/PulsarStandaloneStarter.java

@@ -21,6 +21,7 @@
 import static org.apache.commons.lang3.StringUtils.isBlank;
 
 import java.io.FileInputStream;
+import java.util.Arrays;
 
 import org.apache.pulsar.broker.ServiceConfiguration;
 import org.apache.pulsar.broker.ServiceConfigurationUtils;
@@ -71,8 +72,20 @@ public PulsarStandaloneStarter(String[] args) throws Exception {
         }
 
         // Set ZK server's host to localhost
-        config.setZookeeperServers(zkServers + ":" + this.getZkPort());
-        config.setConfigurationStoreServers(zkServers + ":" + this.getZkPort());
+        // Priority: args > conf > default
+        if (argsContains(args,"--zookeeper-port")) {
+            config.setZookeeperServers(zkServers + ":" + this.getZkPort());
+        } else {
+            if (config.getZookeeperServers() != null) {
+                this.setZkPort(Integer.parseInt(config.getZookeeperServers().split(":")[1]));
+            }
+            config.setZookeeperServers(zkServers + ":" + this.getZkPort());
+        }
+
+        if (config.getConfigurationStoreServers() == null) {
+            config.setConfigurationStoreServers(zkServers + ":" + this.getZkPort());
+        }
+
         config.setRunningStandalone(true);
 
         Runtime.getRuntime().addShutdownHook(new Thread() {
@@ -96,6 +109,10 @@ public void run() {
         });
     }
 
+    private static boolean argsContains(String[] args, String arg) {
+        return Arrays.asList(args).contains(arg);
+    }
+
     public static void main(String args[]) throws Exception {
         // Start standalone
         PulsarStandaloneStarter standalone = new PulsarStandaloneStarter(args);