Remove support of RPAFsetport

ref. https://github.com/gnif/mod_rpaf/issues/12#issuecomment-30717910

> This is a known issue, it is caused by a race condition between
threads setting the virtual host port. A simple way to work around this
would be to run two virtual hosts, one for HTTPS requests, and the
other for HTTP on separate ports. Currently there is no known way to
fix this issue with Apache's internal design.