Racing condition error on cluster join with restricted.cluster.groups set on default project

[victoitor]

Required information

• Distribution: Debian
• Distribution version: 12
• Kernel version: 6.1.0-26-amd64
• Incus version: 6.7
• Storage backend in use: btrfs

Issue description

When trying to join a cluster and the default project is restricted and has restricted.cluster.groups set to a non-default cluster group, joining fails as follows.

Error: Failed to join cluster: Failed to initialize member: Failed to initialize storage pools and networks: Failed to update local member project "default": Invalid project configuration key "restricted.cluster.groups" value: Cluster gr
oup "<non-default cluster group>" doesn't exist                                                                                                                                                                                                                

Cluster join works normally after restricted.cluster.groups is removed on default project.

[stgraber]

Reproduced the issue here, looking at how to reshuffle things to avoid the issue.