Test with abandoning_parent

[asmacdo]

One of the reasons duct was implemented was to poll processes where the parent abandons the child process.

Example test script: https://github.com/con/duct/blob/af67030a40fef7378418d5fa626d6baee7523436/abandoning_parent.sh

[yarikoptic]

don't we test with smth like that already?

[yarikoptic]

while testing this one I think it would be useful to compare against GNU time's report -- does that one track it nicely?

@djarecka used GNU time to track max memory consumption for their investigation.