tls-psk-identity fix

[Alan DeKok]

Kevin Wasserman wrote:
> Currently, the tls-psk-identity attribute is determined while the tls
> connection is established, but then discarded prior to packet decode.
> The attached patch makes the tls-psk-identity attribute available during
> request processing. This is important for implementing constraint
> enforcement policy in Moonshot.

  I've pushed a related fix.  We're trying to lower the number of
#ifdef's in the code.

  Alan DeKok.