Fix listPathRaw/WalkDir cancelation (#11905)

In #11888 we observe a lot of running, WalkDir calls.

There doesn't appear to be any listerners for these calls, so they should be aborted.

Ensure that WalkDir aborts when upstream cancels the request.

Fixes #11888

cmd/metacache-walk.go

@@ -107,6 +107,9 @@ func (s *xlStorage) WalkDir(ctx context.Context, opts WalkDirOptions, wr io.Writ
 	forward := opts.ForwardTo
 	var scanDir func(path string) error
 	scanDir = func(current string) error {
+		if contextCanceled(ctx) {
+			return ctx.Err()
+		}
 		entries, err := s.ListDir(ctx, opts.Bucket, current, -1)
 		if err != nil {
 			// Folder could have gone away in-between
@@ -142,6 +145,9 @@ func (s *xlStorage) WalkDir(ctx context.Context, opts WalkDirOptions, wr io.Writ
 			// Do do not retain the file.
 			entries[i] = ""
 
+			if contextCanceled(ctx) {
+				return ctx.Err()
+			}
 			// If root was an object return it as such.
 			if HasSuffix(entry, xlStorageFormatFile) {
 				var meta metaCacheEntry
@@ -183,6 +189,9 @@ func (s *xlStorage) WalkDir(ctx context.Context, opts WalkDirOptions, wr io.Writ
 			if entry == "" {
 				continue
 			}
+			if contextCanceled(ctx) {
+				return ctx.Err()
+			}
 			meta := metaCacheEntry{name: PathJoin(current, entry)}
 
 			// If directory entry on stack before this, pop it now.