udev/v4l_id: use O_CLOEXEC|O_NOCTTY

This is the usual set of flags. O_CLOEXEC doesn't matter because we don't spawn
anything, but O_NOCTTY could possibly make a difference if the helper is called
on a wrong device type.

src/udev/v4l_id/v4l_id.c

@@ -74,7 +74,7 @@ static int run(int argc, char *argv[]) {
         if (r <= 0)
                 return r;
 
-        fd = open(arg_device, O_RDONLY);
+        fd = open(arg_device, O_RDONLY|O_CLOEXEC|O_NOCTTY);
         if (fd < 0)
                 return log_error_errno(errno, "Failed to open %s: %m", arg_device);