Closes #1680, temporary fix for rpc deadlock inherited from upstream.

src/rpcserver.cpp

@@ -1025,9 +1025,15 @@ void ServiceConnection(AcceptedConnection *conn)
         // Read HTTP message headers and body
         ReadHTTPMessage(conn->stream(), mapHeaders, strRequest, nProto, MAX_SIZE);
 
+        // TODO #1856: Re-enable support for persistent connections.
+        // We have disabled support for HTTP Keep-Alive until resolution of #1680, upstream rpc deadlock.
+        // Close connection immediately.
+        fRun = false;
+        /*
         // HTTP Keep-Alive is false; close connection immediately
         if ((mapHeaders["connection"] == "close") || (!GetBoolArg("-rpckeepalive", true)))
             fRun = false;
+        */
 
         // Process via JSON-RPC API
         if (strURI == "/") {