core/device: avoid bogus errno use and invert ratelimit_test()

core/device: avoid bogus errno use and invert ratelimit_test()

I'm not sure if I understand the original code. AFAICS, errno does not
have to be set at all in this callback.

ratelimit_test() returns positive if we are under limit. The code would only
log if the condition happened very often, which I assume is not inteded, and
this check was supposed to prevent too much logging.