traffic_ctl: get all host statuses by empty arg (#12352)

Author: masaori335

src/traffic_ctl/traffic_ctl.cc

@@ -131,7 +131,7 @@ main([[maybe_unused]] int argc, const char **argv)
   config_command.add_command("registry", "Show configuration file registry", [&]() { command->execute(); })
     .add_example_usage("traffic_ctl config registry");
   // host commands
-  host_command.add_command("status", "Get one or more host statuses", "", MORE_THAN_ONE_ARG_N, [&]() { command->execute(); })
+  host_command.add_command("status", "Get one or more host statuses", "", MORE_THAN_ZERO_ARG_N, [&]() { command->execute(); })
     .add_example_usage("traffic_ctl host status HOST  [HOST  ...]");
   host_command.add_command("down", "Set down one or more host(s)", "", MORE_THAN_ONE_ARG_N, [&]() { command->execute(); })
     .add_example_usage("traffic_ctl host down HOST [OPTIONS]")