Fix: xml: Do not prune leaves from v1 cib diffs that are being created with digests

In lib/cib/cib_utils.c: cib_perform_op(), we validate the created local_diff: 
    test_rc = xml_apply_patchset(c, local_diff, manage_counters);

But if the diff was created with digest, we should not prune leaves from it. Otherwise, the validation in cib_perform_op() would fail.