Successfully using libcurl to do a transfer over a specific HTTP proxy (`proxyA`) with **Digest**...

Successfully using libcurl to do a transfer over a specific HTTP proxy (proxyA) with Digest authentication and then changing the proxy host to a second one (proxyB) for a second transfer, reusing the same handle, makes libcurl wrongly pass on the Proxy-Authorization: header field meant for proxyA, to proxyB.