sesman: Fix PAM authentication on FreeBSD

After recent changes at FreeBSD [1], either PAM_TTY or PAM_RHOST
must be set to authenticate.

[1] http://svnweb.freebsd.org/base?view=revision&amp;revision=271256
Merge pull request #176 from metalefty/v0.6-fix-pam-authentication-on-freebsd

sesman: Fix PAM authentication on FreeBSD