krb5: call krb5_auth_cache_creds() if a password is available
    
    The delayed online authentication feature is only available for password
    authentication and krb5_auth_cache_creds() should only be called if a
    password is available. Otherwise the error coded returned by
    krb5_auth_cache_creds() will prevent proper offline authentication with
    other methods e.g. Smartcard authentication.
    
    Resolves:
    https://pagure.io/SSSD/sssd/issue/3564
    
    Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>