Ensure instance yaml form updates after saving changed yaml

[edlerd]

Done

• Ensure instance yaml form updates after saving changed yaml
• Ensure instance yaml form resets on cancelling changes in the yaml editor

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, run as described here.
2. Perform the following QA steps:
   • edit instance via yaml editor, save changes. ensure editor shows new values
   • edit instance via yaml editor, cancel changes. ensure editor shows old values

[webteam-app]

Demo

Jenkins

demos.haus

[mas-who]

LGTM 👍