Revert "Adapt number of credentials tests executed based on system performance"

This reverts commit 14bc4f381a2299aa7052a4d396185c5d8ab4b87b because
there is not enough benefit from the added complexity compared to
the tests which existed before.
Merge commit '4b0c1b2d2b2cbcc00b3164c3a7e1e09d1d43c0f7' into HEAD