tests/docker: restore TESTS/IMAGES filtering

tests/docker: restore TESTS/IMAGES filtering

This was broken in the re-factor:

  e86c9a64f4 ("tests/docker/Makefile.include: add a generic docker-run target")

Rather than unwind the changes just apply the filters to the total set
of available images and tests. That way we don't inadvertently build
images only not to use them later.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reported-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220225172021.3493923-2-alex.bennee@linaro.org>