fix: prevent settings form input from submitting multiple requests

[mas-who]

Done

• Currently clicking the "Save" button in a setting form input will result in two api requests sent to the server. This PR fixes this issue.

QA

1. Run the LXD-UI:
   • On the demo server via the link posted by @webteam-app below. This is only available for PRs created by collaborators of the repo. Ask @mas-who or @edlerd for access.
   • With a local copy of this branch, build and run as described in the docs.
2. Perform the following QA steps:
   • Go to server settings page, edit any config and save. Observe the network tab in the browser and you should only see one request sending the payload to the lxd server.

[webteam-app]

Demo

Jenkins

demos.haus

[edlerd]

LGTM, thanks for the fix.