ipatests: Update NSSDatabase DBM test on non-DBM-capable installs
    
    The string was updated to include the directory the for the database
    but this was not reflected in the test and not picked up because
    the tests were executed on Fedora 32 which supports dbm so the
    test wasn't executed.
    
    https://pagure.io/freeipa/issue/8675
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Stanislav Levin <slev@altlinux.org>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>