pam: keep pin on the PAM stack for forward_pass
    
    Currently only the password or the long-term part of a two-factor
    authentication was kept on the PM stack if pam_sss.so has the option
    forward_pass. With this patch the Smartcard PIN can be forwarded to
    other PAM modules as well.
    
    Related https://pagure.io/SSSD/sssd/issue/4067
    
    Reviewed-by: Pavel Březina <pbrezina@redhat.com>