LP: #1832176 - Fix release-options directive not adopting defaults correctly

[Caleb-Ellis]

Done

• Moved inline markup in release-options directive to its own partial.
• Renamed a few variables to be clearer (maasReleaseOptions => localOptions, erase => enableDiskErasing).
• Config is now explicitly loaded on directive render. Previously, it was assumed that the config had already been loaded, so refreshing on the node details page would return incorrect config values (i.e. nothing). This also means that a spinner will display when the release dropdown is opened.
• Also fixed a bug where extra parameters weren't actually getting passed to the websocket handler. LOL

QA

• Select multiple machines and choose Release from the action menu, and check that the checkboxes correctly reflect what's set in Settings > Storage. Note that if "Enable disk erasing" is set to true in Settings, the checkbox in the dropdown is disabled and permanently checked by design due to the way the release_or_erase method works in the backend. This took me a liiiittle while to realise that it wasn't a bug that disks were always erased even when the dropdown checkbox suggested otherwise >_>
• Check that running Release actually does what it's supposed to do, e.g. if erase is not selected the node goes straight to "Releasing..." state. If it is selected, the node goes to "Disk erasing..." state.
• Do the same in the node details page.

Fixes

Fixes #562.

Launchpad Issue

lp#1832176.

[steverydz]

LGTM 👍