I have a RPi 3 B with a WiFi dongle. I'd like to connect the built-in RPi WiFi (wlan0) to a wifi router that is not connected to the internet, just local. I'd also like to connect the WiFi dongle (wlan1) to a different WiFi router that is connected to the internet. This I have done, however internet doesn't work unless I disconnect from the local WiFi. Is there a way I can connect to both and have internet?