utils.db: Add missing required param to count_documents
utils.db: Add missing required param to count_documents

New PyMongo API requires filter parameter when counting
documents. Added empty dictionary to satisfy this requirement.

Signed-off-by: Michal Galka <35351e7ebb7262d28d7902253ba30ca44ccd1bb4@collabora.com>

kernelci/kernelci-backend,kernelci/kernelci-backend