you'll need to change the 'fake' supl server's IP address in /etc/hosts to maybe 127.0.0.2.

after making the change, either reboot the device or do:
Btw, the supl proxy does NOT necessarily lead to a gps lock. What it does is to inform your gps/modem about the satelites in your area (without the gps having to find them on its own). the gps must still exchange data with the sats, and if it fails, you're not getting a lock, even though a satelite monitor will show a dozen visible (available) sats