fix: scoutfs etag check for multipart uploads

The Etag can be quoted or not, so the check to verify the part
Etag must remove the quotes before checking for equality. This
check is the same now as posix.

backend/scoutfs/scoutfs.go

@@ -287,7 +287,7 @@ func (s *ScoutFS) CompleteMultipartUpload(ctx context.Context, input *s3.Complet
 		if err != nil {
 			etag = ""
 		}
-		if parts[i].ETag == nil || etag != *parts[i].ETag {
+		if parts[i].ETag == nil || !areEtagsSame(etag, *parts[i].ETag) {
 			return res, "", s3err.GetAPIError(s3err.ErrInvalidPart)
 		}
 
@@ -1025,3 +1025,7 @@ func isNoAttr(err error) bool {
 	}
 	return false
 }
+
+func areEtagsSame(e1, e2 string) bool {
+	return strings.Trim(e1, `"`) == strings.Trim(e2, `"`)
+}