A button "resume download" is needed to finish-up template downloading under images/Templates/zones

##### ISSUE TYPE

* Improvement Request
* Enhancement Request

##### COMPONENT NAME

~~~
UI
~~~

##### CLOUDSTACK VERSION

~~~
4.17.0.1
~~~

##### CONFIGURATION

Advanced Networking

##### OS / ENVIRONMENT

RHEL-7.9

##### SUMMARY

While a template is being uploaded/pushed to a specific zone due to network issues the image/template was not fully downloaded onto that zone. Currently the download percentage is showing as 31%, and even though the management server was bounced yet the download is not getting completed and am looking for a button to resume the download but there is none.

##### STEPS TO REPRODUCE

~~~
step1: Navigate to images/templates and click "Register template from URL"
step2: Fill-up the form to download the template to the desired zone and click OK
step3: While the template is being downloaded - due to network outages or the apache server where qcow2 templates are kept suddenly goes down this will interrupt the template downloading to a specific zone(s).
step4: Once the network outage is resolved, the user should be in a position to "resume download" on images/Templates/zones tab which is NOT available at the moment, hence creating this enhancement request
~~~

##### EXPECTED RESULTS

~~~
As soon as the network issue is resolved, the user should be able to resume the template download by clicking "Resume Download" button.
~~~

##### ACTUAL RESULTS

~~~
there is no button to resume the template download;
~~~


从 images/Templates/zones 标签页开始，按照列出的步骤重现中断的下载，包括网络中断。检查现有的模板下载流程，并确定应如何提供恢复下载的功能；完成的标准是用户在网络恢复后可以点击 "Resume Download"，并且模板下载完成。

由索引模型根据 Issue 内容生成。