qemu user is not added to the user's group when the group doesn't exist

[gbenhaim]

This issue occurs when the group is local (i.e taken from ldap).
We can drop adding qemu user to the user's group and replace it with chmod -R o+x $HOME, or add the users group to the user's /etc/groups (with the same id as the group in ldap).

[gbenhaim]

Since we can't control on the permissions of directories created after lago installation, I think that the best solution will be to inform the user about the issue and let him configure the needed permissions.
Added a fix to lago: lago-project/lago#640