As we can't control which allocations are destroyed when downscaling a job, we decided
to use Nomad jobs as our runners. Thus for each runner we prewarm for an environment,
a corresponding job is created in Nomad. We create a default job that serves as a template
for the runners. Using this, already existing execution environments can easily be restored,
once Poseidon is restarted.
Previously the stderr fifo would not be removed, leaving unwanted
artifacts from the execution behind. We now remove the stderr fifo
after the command finished.
As we pass the context to the Nomad API event stream, they close
the event stream once the passed context is cancelled. We use this
to exit our receive loop on the event stream once the stream is closed,
instead of having to check the context manually.
