Userland: Return 1 when help text is shown for insufficient args

ArgsParser also does this, but we don't use that (yet) in a couple of
places. Fix the behaviour manually for consistency.

Userland/Utilities/flock.cpp

@@ -16,7 +16,7 @@ int main(int argc, char** argv)
 {
     if (argc < 3) {
         warnln("usage: flock <path> <command...>");
-        return 0;
+        return 1;
     }
 
     pid_t child_pid;