Testing of set_config_file function with BATS 2

[matejak]

This PR is a successor to #4656

Differences:

• The cmake setup is simpler, analogous to e.g. linkchecker setup.
• The test that fails has been removed, so the PR can be merged. Another tests can be added later.

[mildas]

@matejak I forgot commit 1 small fix for set_config_file which probably causes failing of that one test scenario.
The problem is here. lineinfile_absent function is called with 3 arguments, so there's no 8th argument. The change should be easy "${8:-true}" -> "${3:-true}". Can you please try it, if with this change the test will pass so we can use it? (sorry, I can't push commit now, otherwise I'd create PR with fix)

[matejak]

@mildas Great point, I have added that fix to the PR.

[matejak]

Seems to work:

       Start  60: bash-unit-tests
59/308 Test  #60: bash-unit-tests ...........................................................   Passed    0.36 sec

[ggbecker]

LGTM, thanks for the patch.