Handle request errors during raft snapshot (#8861)

* Handle request errors during raft snapshot

api/sys_raft.go

@@ -92,6 +92,10 @@ func (c *Sys) RaftSnapshot(snapWriter io.Writer) error {
 	// to determine if the body contains error message.
 	var result *Response
 	resp, err := c.c.config.HttpClient.Do(req)
+	if err != nil {
+		return err
+	}
+
 	if resp == nil {
 		return nil
 	}