ChannelSuite fails when run multiple times

[jczuchnowski]

Noticed a weird behavior that when running test:run multiple times the test hangs. Tracked it down to the ChannelSuite. At some point it hangs with java.net.ConnectException: Connection refused

sbt:scalaz-nio> test:run
[info] Running scalaz.nio.Main 
Testing took 91ms.
[success] Total time: 1 s, completed Apr 23, 2019 2:10:51 AM
sbt:scalaz-nio> test:run
[info] Running scalaz.nio.Main 
Testing took 88ms.
[success] Total time: 0 s, completed Apr 23, 2019 2:10:52 AM
sbt:scalaz-nio> test:run
[info] Running scalaz.nio.Main 
Fail(java.net.ConnectException: Connection refused)