wagon-webdav does not set http-proxy correctly

Webdav connections through a http-proxy are currently not possible.

The webdav provider opens first a connection to the target system and checks after this, if a proxy should be used.

To fix this in the method "org.apache.maven.wagon.providers.webdav.WebdavWagon#openConnection()" the call "webdavResource = new CorrectedWebdavResource( httpURL );" must be changed into "webdavResource = new CorrectedWebdavResource( );" and after configuring the http-proxy the method call "webdavResource.setHttpURL(httpURL);" must be added.