grace_period doesn't honor forward_pass

I was trying to implement `grace_period` with our existing `forward_pass` option to no avail. While `grace_period` itself authenticates without issue with the `LASTIP` option, I believe the full password gets forwarded without being trimmed (see https://github.com/google/google-authenticator-libpam/blob/master/src/pam_google_authenticator.c#L1888 and https://github.com/google/google-authenticator-libpam/blob/master/src/pam_google_authenticator.c#L1923-L1926) which causes the behaviour of `forward_pass` to behave differently.

Was wondering if my suspicion is correct and if so, could someone help with the bug fix?