Merge r1588851 from trunk:

ssl_callback_TmpDH: for OpenSSL 1.0.2 and later, set the current cert to the
one actually used for the connection before calling SSL_get_privatekey(ssl)

Submitted by: kbrand
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1593001 13f79535-47bb-0310-9956-ffa450edef68