mod_proxy_http: follow up to r1853561.

Handle "proxy-sendextracrlf" within the loop too.

Btw, this extra CRLF heresy should go (at least in trunk)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1853566 13f79535-47bb-0310-9956-ffa450edef68