we need this, because we append the port to this to get a target url
e.g. we print
format!("https://{}:8007/", address)
if address is now an ipv6 (e.g. fe80::1) it would become
https://fe80::1:8007/ which is a valid ipv6 on its own
by using square brackets we get:
https://[fe80::1]:8007/ which now connects to the correct ip/port
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>