heal: Remove empty directories (#11354)

Since the introduction of __XLDIR__, an empty directory does not have a
meaning anymore in erasure mode. Make healing removes it wherever it
finds it.

cmd/erasure-server-pool.go

@@ -1359,6 +1359,14 @@ func (z *erasureServerPools) HealObjects(ctx context.Context, bucket, prefix str
 					break
 				}
 
+				// Remove empty directories if found - they have no meaning.
+				// Can be left over from highly concurrent put/remove.
+				if quorumCount > set.setDriveCount/2 && entry.IsEmptyDir {
+					if !opts.DryRun && opts.Remove {
+						set.deleteEmptyDir(ctx, bucket, entry.Name)
+					}
+				}
+
 				// Indicate that first attempt was a success and subsequent loop
 				// knows that its not our first attempt at 'prefix'
 				err = nil