Handle comma-separated list arg to rc.openvpn

The argument passed to rc.openvpn can be a comma-separated list of gateways - not just 1 gateway. Enhance the code to loop and process each gateway.
I have tested this on a simple system disconnecting WAN and connecting it again. The simple case works like it did before. But I don't have a way to generate the complex case where rc.openvpn is passed a comma-separated list of more than 1 gateway name. Someone who can generate such a test case needs to test this and make sure that my argument array processing does actually work.
See forum: http://forum.pfsense.org/index.php/topic,63965.0.html