netns.sh stuck at ncat.

[Jason A. Donenfeld]

This is pretty strange looking, and appears like it's a userland issue
-- like the versions of ncat or ss or whatever weird scripting hacks
in netns.sh aren't working well with the tools installed or some
networking sysctl I forgot to toggle... Maybe one quick way of testing
if it's an ss issue (old RHEL tools, or the like) would be to change
the function body of waitncatudp into just `sleep 2` or something.