net/xrdp: adjust configure arguments

Set --enable-pam-config=freebsd explicitly. If this is not given, PAM
configuration will be autodetected however it might be misdetected on some
environments. Quit relying on autodetection.

Force rebuild because built packages might include misconfigured pam files
as reported in the bugzilla issue..

PR: 248481
Reported by: Sascha Folie <sascha.folie@safo.at>
Sponsored by: HAW International