Not sure of your setup but I use OpenVPN on my Android and have set it to whitelist apps so only the apps that need to use the VPN do so. You can also go the opposite and blacklist so all apps except those you specify use the VPN.

I'm my case, I'm using the OpenVPN server on my router. When I set it up, there was an option for the client to only use the VPN for local traffic. That way it's part of the config file on my phone. Works flawlessly

Try SilverBullet