ipa-backup: adapt for 389ds switch to LMDB
    
    ipa-backup is relying on the presence of the directory
    /var/lib/dirsrv/slapd-<INSTANCE>/db/ipaca/
    to detect if the CA is installed on the server and backup
    the ipaca backend.
    
    With the switch to LMDB, this directory does not exist and the
    backup is missing ipaca information.
    
    Use lib389.cli_ctl.dblib.run_dbscan utility instead to
    check if ipaca backend is present (this method has been
    introduced in 389ds 2.1.0 and works with Berkeley DB and LMDB).
    
    Fixes: https://pagure.io/freeipa/issue/9516
    Signed-off-by: Florence Blanc-Renaud <flo@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Thierry Bordaz <tbordaz@redhat.com>