Add support for checking and submitting HIP reports

Add support for checking and submitting HIP reports

Unlike CSD, the HIP security checker runs during the connection	phase, not
during the authentication phase.

Therefore we need to build the CSD token (an MD5 digest identifying the
client) without relying on the authentication phase having run in the same
process.

We build it from the cookie containing authentication information,
but exclude the volatile field (which changes from session to session)
and the preferred-ip field (which may not be present in all cases, or may
change from session to session).

Signed-off-by: Daniel Lenski <dlenski@gmail.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>