openvpn: add missing host routes

openvpn: add missing host routes

Maintainer: Alexandru Ardelean <redacted>

ping @feckert

First of all big thanks to all involved devs, porting this to proto is not a minor task and besides some small quirks it is working well.
(Not all that happy with the use of a default route instead of /1 routes, because you loose internet if the tunnel goes down but that is just me nitpicking)

However I had problems with default routing as the host routes to the server endpoint were missing.

I tracked it down to code in the `openvpn-hotplug` script and made some changes and in my testing it appears to work now.
As a bonus I also added code for a future implementation of the `nohostroute` option.

Problem:
The host routes were created by just using route setup this however does not work.

Solution:
using `proto_add_host_dependency` seems the better solution.

Furthermore the correct guard for IPv6 seems to be `net_gateway_ipv6` instead of `route_ipv6_gateway` however even the correct guard is only working if ipv6 source routing is disabled on wan6, so perhaps we should consider removing the guard entirely.
For now I left it in place with a warning.

I have tested it on X86 running master build from 5 days ago, both for IPv4 and IPv6

Please have a look and consider implementing.

Thanks

Signed-off-by: Erik Conijn <redacted>