SSL: adjusted session id context with dynamic certificates. Dynamic certificates re-introduce problem with incorrect session reuse (AKA "virtual host confusion", CVE-2014-3616), since there are no server certificates to generate session id context from. To prevent this, session id context is now generated from ssl_certificate directives as specified in the configuration. This approach prevents incorrect session reuse in most cases, while still allowing sharing sessions across multiple machines with ssl_session_ticket_key set as long as configurations are identical.