shared/verbs: stop requiring an explicit program name

Almost all programs are simple and have only a single command. When
printing options, let's just use the first COMMAND block found by default.
This means we can drop the explicit program-name argument and reduce
copy&paste boilerplate.

src/mstack/mstack-tool.c

@@ -70,7 +70,7 @@ static int parse_argv(int argc, char *argv[]) {
                 OPTION_GROUP("Commands"): {}
 
                 OPTION_COMMON_HELP:
-                        return command_print_help("systemd-mstack");
+                        return command_print_help();
 
                 OPTION_COMMON_VERSION:
                         return version();