fix: make sure to avoid calling RenameData() on disconnected disks. (#14094)

Large clusters with multiple sets, or multi-pool setups at times might
fail and report unexpected "file not found" errors. This can become
a problem during startup sequence when some files need to be created
at multiple locations.

- This PR ensures that we nil the erasure writers such that they
  are skipped in RenameData() call.

- RenameData() doesn't need to "Access()" calls for `.minio.sys`
  folders they always exist.

- Make sure PutObject() never returns ObjectNotFound{} for any
  errors, make sure it always returns "WriteQuorum" when renameData()
  fails with ObjectNotFound{}. Return appropriate errors for all
  other cases.

cmd/erasure-healing.go

@@ -540,7 +540,7 @@ func (er erasureObjects) healObject(ctx context.Context, bucket string, object s
 
 			// If all disks are having errors, we give up.
 			if disksToHealCount == 0 {
-				return result, fmt.Errorf("all disks had write errors, unable to heal")
+				return result, fmt.Errorf("all disks had write errors, unable to heal %s/%s", bucket, object)
 			}
 
 		}