add tests for empty otp part to check_user_token()
add tests for empty otp part to check_user_token()

eworm-de/yubico-pam,eworm-de/yubico-pam,eworm-de/yubico-pam,Yubico/yubico-pam,Yubico/yubico-pam,Yubico/yubico-pam