Revert "using ApacheHttpClient4 too get rid of dependency to deprecated ...

As suggested by @MichaelKunze and @gsteinacker: reverting "using ApacheHttpClient4 too get rid of dependency to deprecated org.apache.commons.httpclient.HttpClient"

This reverts commit 5184155df8fd0aa298005813b270dd175f04ed7e.

This was necessary since ApacheHttpClient4 always sends requests with chunked encoding, and this lets Varnish puke, since he is not able to handle request with chunked encoding.