Fix d2i_SSL_SESSION for DTLS1_BAD_VER

Some Cisco appliances use a pre-standard version number for DTLS. We support
this as DTLS1_BAD_VER within the code.

This change fixes d2i_SSL_SESSION for that DTLS version.

Based on an original patch by David Woodhouse <dwmw2@infradead.org>

RT#3704

Reviewed-by: Tim Hudson <tjh@openssl.org>