mpm_winnt: remove duplication of ap_process_connection

Further follow-up to the previous commit: now that we no longer patch a
network bucket into the brigade, we can revert to calling
ap_process_connection() directly instead of duplicating its logic.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1758309 13f79535-47bb-0310-9956-ffa450edef68