Downloading Template Failed

##### ISSUE TYPE

* Bug Report

##### COMPONENT NAME
UI

##### CLOUDSTACK VERSION
CloudStack 4.19.1.3

##### OS / ENVIRONMENT
Ubuntu
KVM

##### SUMMARY
I can not Download Any Image Template

##### STEPS TO REPRODUCE
1- Create Template Template From any Instance
2- Image -> Template -> Download Template
3- I get Image Template Download Link With IP Address Of Secondary Storage VM But it Returned "The requested URL was not found on this server."
4- When I check SecondaryStorage SYSVM in /var/www/html/userdata PATH it does not provide any file for the image template and is null

##### EXPECTED RESULTS
I want to download my image template
##### ACTUAL RESULTS
After creating the download link, I got the following message: "The requested URL was not found on this server."

在 UI 中使用所报告的 CloudStack 4.19.1.3、Ubuntu 和 KVM 环境复现模板下载流程。首先检查生成的链接和 Secondary Storage VM 的 /var/www/html/userdata 路径；当模板文件可用且其下载链接不再返回 not-found 错误时，工作即完成。

由索引模型根据 Issue 内容生成。