rgw: EPERM to ERR_INVALID_REQUEST

As per Robin's comments and S3 spec

Signed-off-by: Abhishek Lekshmanan <abhishek@suse.com>

src/rgw/rgw_rest_s3.cc

@@ -301,7 +301,7 @@ int RGWGetObj_ObjStore_S3::send_response_data(bufferlist& bl, off_t bl_ofs,
 	/* reject unauthenticated response header manipulation, see
 	 * https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetObject.html */
 	if (s->auth.identity->is_anonymous()) {
-	  return -EPERM;
+	  return -ERR_INVALID_REQUEST;
 	}
 	if (strcmp(p->param, "response-content-type") != 0) {
 	  response_attrs[p->http_attr] = val;