PAM: Use the override_space option
    
    https://fedorahosted.org/sssd/ticket/2397
    
    When using the override_default_space option, this patch allows to log
    in using both the original name (space user) as well as the normalized
    name (space_user).
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>