All tests in /usr/libexec/tests/osbuild-composer should be able to run without
any arguments. This was not a case of libvirt.sh - it required two arguments
set by some Jenkinsfile logic.
This commit moves test/cases/libvirt.sh to tools/libvirt_test.sh and extracts
the logic controlling the test case from Jenkinsfile to test/cases/libvirt.sh.
Signed-off-by: Ondřej Budai <ondrej@budai.cz>
