[backend] add ipv6 support for workers

[YukariChiba]

Currently OBS does not support workers connected from IPv6.
This commit enables BSRPC to parse IPv6 hosts, which allows jobs to be dispatched via IPv6.

(Tested on self-hosted OBS instance for eweOS)

[adrianschroeter]

thanks, but please add the [backend] tag in commit message

[mlschroe]

Wouldn't you need to write IO::Socket::IP->join_addr? (But I don't think we really need this just to put the host in [] if it includes a : character...)

[YukariChiba]

Wouldn't you need to write IO::Socket::IP->join_addr? (But I don't think we really need this just to put the host in [] if it includes a : character...)

Resolved. Now it's implemented without using IO::Socket::IP.