PAM auth doesn't work on OpenBSD

[rdmark]

When attempting to dynamically authenticate with PAD enabled UAMs on OpenBSD, an internal error is thrown:

afpd[61380] {uams_dhx2_pam.c:658} (info:UAMS): DHX2: PAM_Error: System error

This behavior is the same on 3.2 as well as bleeding edge 4.2. In fact, the 3.1.18 package distributed by OpenBSD supplies only basic passwd auth, and is not built with PAM. This might never have worked.