Switch credits from toolserver to wmflabs. It must use the internal proxy as wmflabs.org can't be reached from inside wmflabs.org so we use http://tools-webproxy. The drawback is that tools-webrproxy can't be reached from outside wmflabs, so credits works only from the wmflabs site. Other wsexport site than the wmflabs one will wait for a timeout for credits and get empty credits.