Cluster: Add --status-only flag to lxc cluster restore command

[gabrielmougard]

JIRA ticket: https://warthogs.atlassian.net/browse/LXD-2602?atlOrigin=eyJpIjoiOGUwYzQ5ODJmZjNkNGEyMzk4MTlmN2ZhZWY1YWM5MzciLCJwIjoiaiJ9

This adds a --status-only flag to the lxc cluster restore command, which allows a cluster member to be restored to the online state without affecting any instances.

Problem

When a node is evacuated and then restored using lxc cluster restore:

• Instances with local storage that were stopped during evacuation are automatically restarted.
• Instances with remote storage that were migrated to other nodes are automatically migrated back.

We may want to restore just the node's status to online without affecting the current state and location of instances.

Solution

Added a new --status-only flag to the lxc cluster restore command that:

• Does NOT restart any local instances that were stopped.
• Does NOT migrate back any instances that were evacuated to other nodes.

API extension

Added clustering_restore_member_only API extension

Testing

• Restoring a node with local and remote storage instances using the --status-only flag
• Verifying that instances remain in their evacuated state/location after restore.
• Confirming that a standard restore without the flag exhibits the original behavior.

[tomponline]

Looks pretty good, there's a few code cleanups and optimisations we can do thought whilst we looking at this code.

[tomponline]

also needs a rebase please

[minaelee]

Copyedit suggestion + suggestion about flag naming.

[minaelee]

Thanks for changing member-only to status-only.
I am still seeing multiple places where member_only is used, seems like those should also be updated to status_only.

[gabrielmougard]

Thanks for changing member-only to status-only.
I am still seeing multiple places where member_only is used, seems like those should also be updated to status_only.

should be fixed :)

[minaelee]

I see a couple more instances of memberOnly

[tomponline]

please rebase

[tomponline]

LGTM!

[minaelee]

lgtm, ty (for docs/naming anyway - I see there are test failures)

[tomponline]

tests look flaky

[gabrielmougard]

hmm yes. I'm trying to understand why.