Ansible 2.3/Python 2.4 work revealed there is no guarantee a slow target
will have written the initial job status file out before a fast
controller makes an initial check for it. Therefore, provide AsyncRunner
with a sender it should send a message to when the initial job file has
been written.
As a bonus, also catch and report exceptions happening early in
AsyncRunner, rather than leaving them to end up in -vvv output.
David Wilson