console does not attach if domain exits too quickly

[anttikantee]

In case the domain hits an err() or something similar early in the execution, xl create -c domain_config does not display anything useful. I assume the same applies to running the guest via rumprun -i.

It's probably a Xen tool race condition, although I'm not 100% sure.

As a workaround, I added a sleep(1) along the exit(error) path:
9bc666a

The purpose of this issue is mostly to remind us that in case we want really short-lived guests in a production case some day, at least the console cannot be relied on.