tests: filters: Implement compare tests.

The tests runs the same filter using different APIs and compares
results, fails if resulting contexts does not match.

Signed-off-by: Cyril Hrubis <metan@ucw.cz>
tests: filters: Better API Converage test.

* More filters covered

* Now with checks for correct errno values

Signed-off-by: Cyril Hrubis <metan@ucw.cz>