Issue #16 : chef-init doesn't adopt orphaned child

Code for cleaning up terminated process.
See issue https://github.com/opscode/chef-init/issues/16 for details.
It isn't necessarily a problem, but it seems weird to me that we are going to store the status of every pid we might reap.  But, this keeps the function pretty general.  It will have an impact on memory usage for long running containers that generate zombies we have to reap, but I don't think we need to worry too much about that.