Shield could not restore itself through webUI for the case of shield itself is down.

[xiujiao]

Describe the bug
When the shield is down, I spin up a new shield, then try to restore the old shield to the new shield.
In Web UI, I click upload backup file, after I select a file, click upload, it does not do anything. It did not upload.

To Reproduce

1. Deploy shield 8.7.2, configured some jobs including backup shield itself through metashield plugin
2. Deploy shield 8.7.3
3. Restore shield 8.7.3 using backup taken from shield 8.7.2 in web UI

Expected behavior
The backup file should be uploaded successfully and restore.
The new shield should have the same configurations with the old one after restore.

Browser version(s) (please complete if reporting a web UI bug):

• OS: OSX
• Browser: tried chrome andsarifi