This feature also cleans up and extends the meta subsystem:
* Allows for some meta actions (noop, clear_facts, clear_host_errors,
and end_play) to operate on a per-host basis, meaning they can work
with the free strategy as expected.
* Allows for conditionals on meta tasks.
* Fixes a bug where (for the linear strategy) metas were not treated
as a run_once task, meaning every host in inventory would run the
meta task.
Fixes#1476
78b8f81cab