fix: do not return an error for successfully deleted dangling objects (#10938)

dangling objects when removed `mc admin heal -r` or crawler
auto heal would incorrectly return error - this can interfere
with usage calculation as the entry size for this would be
returned as `0`, instead upon success use the resultant
object size to calculate the final size for the object
and avoid reporting this in the log messages

Also do not set ObjectSize in healResultItem to be '-1'
this has an effect on crawler metrics calculating 1 byte
less for objects which seem to be missing their `xl.meta`

cmd/erasure-object_test.go

@@ -19,6 +19,7 @@ package cmd
 import (
 	"bytes"
 	"context"
+	"errors"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -257,7 +258,7 @@ func TestErasureDeleteObjectDiskNotFound(t *testing.T) {
 	z.serverSets[0].erasureDisksMu.Unlock()
 	_, err = obj.DeleteObject(ctx, bucket, object, ObjectOptions{})
 	// since majority of disks are not available, metaquorum is not achieved and hence errErasureWriteQuorum error
-	if err != toObjectErr(errErasureWriteQuorum, bucket, object) {
+	if !errors.Is(err, errErasureWriteQuorum) {
 		t.Errorf("Expected deleteObject to fail with %v, but failed with %v", toObjectErr(errErasureWriteQuorum, bucket, object), err)
 	}
 }
@@ -381,7 +382,7 @@ func TestPutObjectNoQuorum(t *testing.T) {
 		z.serverSets[0].erasureDisksMu.Unlock()
 		// Upload new content to same object "object"
 		_, err = obj.PutObject(ctx, bucket, object, mustGetPutObjReader(t, bytes.NewReader([]byte("abcd")), int64(len("abcd")), "", ""), opts)
-		if err != toObjectErr(errErasureWriteQuorum, bucket, object) {
+		if !errors.Is(err, errErasureWriteQuorum) {
 			t.Errorf("Expected putObject to fail with %v, but failed with %v", toObjectErr(errErasureWriteQuorum, bucket, object), err)
 		}
 	}