Interrupt to run post test workers

[AdamWHuffman]

I have implemented multiple pre and post test plugins to support various hosts.

When I run avocado run <test> -m <muxfile> for example, then I send an interrupt, I would like a way to run all of the post test workers so that my assets are cleaned up. These assets include hosts like ansible-created VMs that are left running.

An alternative is signal handlers inside of my plugins, but this causes quite a few issue as they must ignore the signals from the base avocado workers.

This may already be possible with configurations, but I have not yet found the option.