Hijk Tests Hang for Days

Since the v0.28 release, our RPM building job has been hanging for days at a time on the Hijk tests. Output:

```
- Building Hijk-0.28
2019/01/16-08:42:53 main (type Net::Server::HTTP -> MultiType -> Net::Server::PreFork) starting! pid(8435)
Resolved [*]:13796 to [::]:13796, IPv6
Not including resolved host [0.0.0.0] IPv4 because it will be handled by [::] IPv6
Binding to TCP port 13796 on host :: with IPv6
Group Not Defined. Defaulting to EGID '1999 135 1999'
User Not Defined. Defaulting to EUID '489'
2019/01/16-08:42:55 Server closing!
HTTP::Server::PSGI: Accepting connections at http://0:14492/
# Connecting to a wrong port: 14492
# Dying message: Connection refused at /home/jenkins-slave/workspace/CentOS6-Perl-5.20/BUILD/Hijk-0.28/blib/lib/Hijk.pm line 289.
127.0.0.1 - - [16/Jan/2019:08:43:10 -0800] "GET /?t=5 HTTP/1.1" 200 32 "-" "-"
127.0.0.1 - - [16/Jan/2019:08:43:15 -0800] "GET /?t=5 HTTP/1.1" 200 33 "-" "-"
```

And it's just stopped there, hanging out, nothing happening. I was unable to replicate when building manually; could there be something waiting on a TTL or something?