acpi/tests/avocado/bits: enable bios bits avocado tests on gitlab CI pipeline

Biosbits avocado tests on gitlab has thus far been disabled because some
packages needed by this test was missing in the container images used by gitlab
CI. These packages have now been added with the commit:

da900078 ("tests/lcitool: Add mtools and xorriso and remove genisoimage as dependencies")

Therefore, this change enables bits avocado test on gitlab.
At the same time, the bits cleanup code has also been made more robust with
this change.

Signed-off-by: Ani Sinha <anisinha@redhat.com>
Message-Id: <20230517065357.5614-1-anisinha@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>