* Add 'cacheable' param to set_fact action and module.
Used just like set_fact, except facts set with cacheable: true
will be stored in the fact cache if fact caching is enabled.
set_fact normally only sets facts in the non_persistent_fact_cache, so they
are lost between invocations.
* update set_facts docs
* use 'ansible_facts_cacheable' in module/actions result
* pop fact cacheable related items out of args/results
We dont want to use 'ansible_facts_cacheable' result item
or 'cacheable' arg as actual facts, so pop them out of the
dicts.
