Add reneg-sec param as a modifiable attribute in chef.

[Darkdoughnut]

Hey! So we've been trying to implement 2fa using openvpn and one critical setting for us is the reneg-sec which sets the timeout timer for connections. Currently it's set at 8 hours but I think it would be nice to make this a configurable attribute.

[ramereth]

@Darkdoughnut if you create a PR which implements this, we can certainly review it and get it merged in!