Increase network i/o capacity.

Author: mtrippled

src/xrpld/app/main/Application.cpp

@@ -256,8 +256,8 @@ class ApplicationImp : public Application, public BasicApp
         if ((cores == 1) || ((config.NODE_SIZE == 0) && (cores == 2)))
             return 1;
 
-        // Otherwise, prefer two threads.
-        return 2;
+        // Otherwise, prefer six threads.
+        return 6;
 #endif
     }