can't connect over HTTP_PROXY env with auth
Bug description
by using HTTP_PROXY variable with password, the password isn't set right and not used for the connection
Steps to reproduce
activate HTTP_PROXY environment variable (HTTP_PROXY='http://user:password@proxy:port') for an account and connect
gajim.c.x.proxy_connectors: Invalid proxy reply: HTTP/1.1 407 Proxy Authentication Required