Validate prefixes on all sets (#6294)

This PR fixes a regression introduced in 8eb838bf91
where hashing technique was used on prefixes to get the right set
to perform the operation, this is not correct since prefixes and
their corresponding keys might hash to a different value depending
on the key length.

For prefixes/directories we should look everywhere to support proper
quorum based listing.

Fixes #6293

cmd/xl-sets.go

@@ -714,7 +714,15 @@ func (s *xlSets) ListObjects(ctx context.Context, bucket, prefix, marker, delimi
 		}
 
 		isLeafDir := func(bucket, entry string) bool {
-			return s.getHashedSet(entry).isObjectDir(bucket, entry)
+			// Verify prefixes in all sets.
+			var ok bool
+			for _, set := range s.sets {
+				ok = set.isObjectDir(bucket, entry)
+				if ok {
+					return true
+				}
+			}
+			return false
 		}
 
 		var setDisks = make([][]StorageAPI, len(s.sets))
@@ -742,7 +750,13 @@ func (s *xlSets) ListObjects(ctx context.Context, bucket, prefix, marker, delimi
 		var objInfo ObjectInfo
 		var err error
 		if hasSuffix(walkResult.entry, slashSeparator) {
-			objInfo, err = s.getHashedSet(walkResult.entry).getObjectInfoDir(ctx, bucket, walkResult.entry)
+			// Verify prefixes in all sets.
+			for _, set := range s.sets {
+				objInfo, err = set.getObjectInfoDir(ctx, bucket, walkResult.entry)
+				if err == nil {
+					break
+				}
+			}
 		} else {
 			objInfo, err = s.getHashedSet(walkResult.entry).getObjectInfo(ctx, bucket, walkResult.entry)
 		}
@@ -1349,7 +1363,14 @@ func (s *xlSets) listObjectsHeal(ctx context.Context, bucket, prefix, marker, de
 		}
 
 		isLeafDir := func(bucket, entry string) bool {
-			return s.getHashedSet(entry).isObjectDir(bucket, entry)
+			var ok bool
+			for _, set := range s.sets {
+				ok = set.isObjectDir(bucket, entry)
+				if ok {
+					return true
+				}
+			}
+			return false
 		}
 
 		var setDisks = make([][]StorageAPI, len(s.sets))