Fix hangs when type invalid args at command-line (apache#5615)

Fixes apache#5533 

*Motivation*

When we using command-line tools, it hangs after type an invalid args.

*Modifications*

We don't need to parse the command, just show the command usage.

pulsar-client-tools/src/main/java/org/apache/pulsar/admin/cli/CmdBase.java

@@ -39,14 +39,23 @@ public CmdBase(String cmdName, PulsarAdmin admin) {
         jcommander.setProgramName("pulsar-admin " + cmdName);
     }
 
+    private void tryShowCommandUsage() {
+        try {
+            String chosenCommand = jcommander.getParsedCommand();
+            jcommander.usage(chosenCommand);
+        } catch (Exception e) {
+            // it is caused by an invalid command, the invalid command can not be parsed
+            System.err.println("Invalid command, please use `pulsar-admin --help` to check out how to use");
+        }
+    }
+
     public boolean run(String[] args) {
         try {
             jcommander.parse(args);
         } catch (Exception e) {
             System.err.println(e.getMessage());
             System.err.println();
-            String chosenCommand = jcommander.getParsedCommand();
-            jcommander.usage(chosenCommand);
+            tryShowCommandUsage();
             return false;
         }