Support OpenSSL 1.1.0:

- Fix renegotiation for the client side
  of a proxy connection.

Backport of r1730146 from trunk.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x-openssl-1.1.0-compat@1755835 13f79535-47bb-0310-9956-ffa450edef68