CI testing: Fix the SRPM download
    
    Usually, this test is used for gating ltrace.  In such case the
    Fedora infrastructure offers the SRPM along with other ltrace
    subrpms within a repo called "test-artifacts".
    
    However, this test is also used to test dejagnu, because ltrace
    has dejagnu based testsuite.  In such case the "test-artifacts"
    repo has dejagnu, but not ltrace.
    
    We need to be able to get the ltrace SRPM in both cases.