mod_proxy_hcheck: take balancer's SSLProxy* directives into account.

mod_proxy_hcheck was missing the merge of SSLProxy* directives defined by
balancer with the ones of the VirtualHost.

Since ap_proxy_connection_create_ex() needs a merged r->per_dir_config to apply
the correct SSL configuration, let's split create_request_rec() in two:
- create_request_rec() to only initialize the non-connection fields and merge
  balancer->section_config into r->per_dir_config,
- set_request_connection() to associate the connection with the request once
  it's been created from the merged configuration of the minimal request.

The issue was reported on the users@ mailing list:
https://lists.apache.org/thread.html/895cf250104b081b789101b1086b71a26d9c337db7123c5a552b7c69@%3Cusers.httpd.apache.org%3E


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1836276 13f79535-47bb-0310-9956-ffa450edef68