Test dlz support in feature-test

dlz system test is failing in our Fedora builds. That is because we make special variant with sdb support, normal build does not have such features. Because prereq.sh is common for whole build, it cannot make difference between them. This is part of fix we can use on Fedora, I think it is useful also for others.

What about support was moved into feature-test, where most similar tests are done?