ldap: use proper sysdb name in groups_by_user_done()
    
    In a recent change set_initgroups_expire_attribute() was added to
    groups_by_user_done() to make sure that the initgroups timeout is only
    added to the user object until all groups added to the cache.
    
    This change (and the original code in groups_by_user_done() as well)
    didn't took sub-domain users into account where the name in sysdb might
    different form the original request and the domain is not the configured
    domain. This patch tries to ensure that the right name and domain are
    used.
    
    https://fedorahosted.org/sssd/ticket/2663
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>