add healing fixes for delete-marker (#12788)

- delete-markers are incorrectly reported
  as corrupt with wrong data sent to client
  'mc admin heal -r' on objects with delete
  marker will report as 'grey' incorrectly.

- do not heal delete-markers during HeadObject()
  this can lead to inconsistent order of heals
  on the object, although this is not an issue
  in terms of order of versions it is rather
  simpler to keep the same order on all drives.

- defaultHealResult() should handle 'err == nil'
  case such that valid cases should be handled
  as 'drive' status OK.

cmd/erasure-object.go

@@ -442,7 +442,9 @@ func (er erasureObjects) getObjectFileInfo(ctx context.Context, bucket, object s
 	}
 
 	// if missing metadata can be reconstructed, attempt to reconstruct.
-	if missingBlocks > 0 && missingBlocks < readQuorum {
+	// additionally do not heal delete markers inline, let them be
+	// healed upon regular heal process.
+	if !fi.Deleted && missingBlocks > 0 && missingBlocks < readQuorum {
 		if _, healing := er.getOnlineDisksWithHealing(); !healing {
 			go healObject(bucket, object, fi.VersionID, madmin.HealNormalScan)
 		}