Introduce domain deletion check
Add a new method, bolt_domain_can_delete
, which can be used to
check if a domain can safely be deleted without the loss of data.
Currently, the only case where this can happen if the boot acl
journal for the domain has entries.
Then use this new method to check if a domain can be safely deleted
before doing so. In the case it is not safe to delete the domain,
the bolt_store_del_domain
method will now return FALSE
and
propagate the error from domain_can_delete.