* use tower-expect command to determine job status when running
the isolated heartbeat playbook
* grok JSON output of playbook to obtain result information
* run playbook against multiple isolated hosts at the same time
(addresses scalability concerns)
Previously we were running the playbook on a host-by-host
basis, but this changes it to pass in the list of all
isolated isntances the machine is responsible for.
Using the `json` Ansible stdout module, we are able to
parse the output for information on each host.
* set a more reasonable default `AWX_ISOLATED_CHECK_INTERVAL`
* make manual cancellation work for high values of
`AWX_ISOLATED_CHECK_INTERVAL`
* remove the `/tmp/ansible_tower/jobs/` symlink directory
see: #6616
instead of launching isolated tasks via `systemctl`, treat
`awx.main.isolated.run` as an executable that knows how to daemonize
additionally, add `setup.py isolated_build` for isolated Tower source
distribution
