[bug](user login)fix PASSWORD_LOCK_TIME setting UNBOUNDED does not take effect (#26585)

fe/fe-core/src/main/java/org/apache/doris/mysql/privilege/PasswordPolicy.java

@@ -410,7 +410,8 @@ public class PasswordPolicy implements Writable {
             }
             if (lockTime.get() > 0 && passwordLockSeconds == UNBOUNDED) {
                 // unbounded lock
-                return 0;
+                // Returns 9999 seconds every time instead of 9999 seconds countdown
+                return 9999;
             }
             return Math.max(0, passwordLockSeconds - ((System.currentTimeMillis() - lockTime.get()) / 1000));
         }