ProtocolServer: Run with low priority

Dr. Bugaev says this is the most appropriate priority. :^)

Base/etc/SystemServer.ini

@@ -2,6 +2,7 @@
 Socket=/tmp/portal/protocol
 SocketPermissions=660
 Lazy=1
+Priority=low
 User=protocol
 BootModes=text,graphical
 MultiInstance=1