2016235 IPA: Do not allow the AD lookup code to set backend as offline in server mode

Authored and Committed by jhrozek 8 years ago
    IPA: Do not allow the AD lookup code to set backend as offline in server mode
    
    https://fedorahosted.org/sssd/ticket/2637
    
    In server mode, we should not allow the AD lookups to set the backend
    offline. Rather just let them report an error and deal with the error
    separately.
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>