udp6/tcp6 combined with IPv4 address in client configuration

If a user check Listen on IPv6 it generates proto udp6 or tcp6 to client configuration files. But remote still contains an IPv4 address. This configuration won't work because it can't resolve IPv4 addresses for IPv6 communication.

Steps to reproduce

1. Check Listen on IPv6 on the OpenVPN -> Server Settings page.
2. Generate a client configuration on the OpenVPN -> Client Registration page.
3. Download the configuration and use it in an OpenVPN client.

Expected behavior

Unfortunately, it can't be determined what Listen on IPv6 exactly means (whether IPv4 should be used or not). Because of this, there can be two distinct ways how to work with it.

IPv6 without IPv4

The checkbox should be available only if IPv6 is enabled and working. If checked, it should generate proto udp6/tcp6 together with an IPv6 address in remote.

IPv4 + IPv6

Another option should be available to choose which protocol to be used. It should generate proto and remote for the selected protocol.

Actual behavior

According to the checkbox state, proto contains udp/tcp or udp6/tcp6. Regardless to the checkbox state, remote contains an IPv4 address.