[bug] wireguard-android does not correctly add resolved IPv6 endpoints

[Alex Xu]

description:

Using wireguard android 2018.12.18 on an IPv6-only network, it is not
possible to use a DNS name for an endpoint.

steps to reproduce:

1. create a tunnel. set the endpoint to example.com:12345
2. bring up the tunnel

expected results:

the tunnel is brought up (in this case it won't actually work because
example.com is not a wireguard server, but it will be brought up)

actual results:

In the log, there is this error:

WireGuard/GoBackend/wg0: Failed to set endpoint: x:x:x:x::1:40257

additional information:

entering the same IP address with square brackets works fine.