backport r1211352 from trunk:

Adjust the OpenSSL session id context for SNI configurations, so that
sessions are tied to the proper vhost (subset of a patch I originally
proposed in November 2009, cf. message with ID <4AF85A18.1000205@velox.ch>).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1211353 13f79535-47bb-0310-9956-ffa450edef68