On JRuby it seems that Socket#connect call is not abortable by Timeout.timeout nor by Thread.kill. Bug report: https://github.com/jruby/jruby/issues/6126

If the connect call gets so stuck, our monitoring thread does not die (seemingly ever). This causes some of the subsequent tests to fail because there is a running background thread.

Consider a thread that is aborting to be dead as a workaround.