Optimise usage of setLoading/setSubmitting functions

[lorumic]

Done

• Optimised usage of setLoading(false) and setSubmitting(false) throughout the app, following these criteria:
  • In the general case or when there's only a notification with no navigation, setLoading/setSubmitting should be called inside the finally block.
  • When there's navigation, setLoading/setSubmitting should be called inside the catch block (not needed for the success block as we navigate).
• Removed some duplicates (e.g. calls to setLoading in the success block when there was already a call in the finally block).

Files affected by #506 are intentionally excluded from the scope of this PR.

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 @lorumic or @edlerd for access.
   • With a local copy of this branch, run as described here.
2. Perform the following QA steps:
   • Check that all the affected buttons look and behave as expected

[webteam-app]

Demo starting at https://lxd-ui-508.demos.haus

[edlerd]

LGTM