contents: real previous node from zone search

Don't require the node to be authoritative. This is need for DNSSEC
proofs and this should be handled there.

src/knot/zone/zone-tree.c

@@ -118,12 +118,6 @@ int zone_tree_get_less_or_equal(zone_tree_t *tree,
 		hattrie_iter_free(i);
 	}
 
-	/* Previous node for proof must be non-empty and authoritative. */
-	if (*previous &&
-	    ((*previous)->rrset_count == 0 || (*previous)->flags & NODE_FLAGS_NONAUTH)) {
-		*previous = (*previous)->prev;
-	}
-
 	return exact_match;
 }