Bug 4581: Secure ICAP segfault in checkForMissingCertificates

Bug 4581: Secure ICAP segfault in checkForMissingCertificates

The Security::PeerConnector::request member is NULL in the case of secure
ICAP. This patch checks if this member is NULL before using it.

Also fixes Security::PeerConnector to send to cert validator the correct
domain name. Curretly sends the host name from the HttpRequest object, which
is not correct not only for secure ICAP cases (where this object does not
exist), but also for the cases where squid connecting to a remote proxy
using TLS.

This is a Measurement Factory project