Can't bind to specific IPv6 interface

If I start the server like this:
```
nimblex:~# ./nettest-linux-x86_64/nettest -s -l [fe80::1706:fb83:8249:73d0]:334
Reading config from: "/etc/nettest.conf"
Error: Os { code: 22, kind: InvalidInput, message: "Invalid argument" }

```
It fails to bind to a specific IPv6 interface. I can't reproduce this issue with IPv4.