Set CURLOPT_FORBID_REUSE for XMLRPCResponder

XMLRPCResponder is used to login, which is a HTTP 1.0 server
that doesn't support reuse of connections.
It's cleaner to close connections from our side too.

This changes,
0x7fffdcf93700   CURLIO      0x7fffcd86db40   * Connection #0 to host login.agni.lindenlab.com left intact
into
0x7fffdcf93700   CURLIO      0x7fffcd8b0bd0   * Closing connection #0

indra/llmessage/aicurl.cpp

@@ -1392,6 +1392,10 @@ void BufferedCurlEasyRequest::prepRequest(AICurlEasyRequest_wat& curl_easy_reque
 	// to id.secondlife.com for marketplace.secondlife.com.
 	allow_cookies = true;
   }
+  if (responder->forbidReuse())
+  {
+	curl_easy_request_w->setopt(CURLOPT_FORBID_REUSE, 1);
+  }
   if (allow_cookies)
   {
 	// Given an empty or non-existing file or by passing the empty string (""),