MFC: r269875
MFC: r269875

According to opie code and even direct mention in opie(4) challenge buffer
size must be OPIE_CHALLENGE_MAX + 1, not OPIE_CHALLENGE_MAX

Reviewed by:    des

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase