Fix two bugs in ab:

1) The Host: header was not filled in correctly (it used the proxyhost,
   not the destination host), and
2) on POST requests, the wrong path was used.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@88813 13f79535-47bb-0310-9956-ffa450edef68