Fix nested iteration of openvpn_clients.

[johngian]

No description provided.

[johngian]

This fixes an issue triggered after my last deployment with ansible 2.5.1.

The paths when running this [1] task were wrong. Instead of iterating over the openvpn_clients values, it replaced the path with the string openvpn_clients which didn't exist.

[1] https://github.com/sovereign/sovereign/blob/master/roles/vpn/tasks/openvpn.yml#L169

[Titan-C]

I had this problem a while back. I thought to have done a PR too, but it is just on my local version.
+1 for merge.

[neuhaus]

Thanks!