Ticket 49432 - filter optimise crash
    
    Bug Description:  In a certain condition with a filter, when we
    removed the equality candidate to optimise it, with a nested
    and, during the merge process we would segfault
    
    Fix Description:  Fix the merge subfilter process to be cleaner
    and work in all conditions. Merge the set of filter tests to
    cmocka in addition to the python tests to help catch this earlier
    
    https://pagure.io/389-ds-base/issue/49432
    
    Author: wibrown
    
    Review by: mreynolds (Thanks!)
    
    (cherry picked from commit 5c89dd8f9c8eb77c967574412d049d55565bb364)