Use the Mistral directory for storing the Ansible fact cache.
Use the Mistral directory for storing the Ansible fact cache.

This aligns with how TripleO currently stores all Ansible data
in /var/lib/mistral/. Our documentation already recommends
running setfacl on that directory if an end-user wants to
access the files there.

Change-Id: I29d0a353cd0a0d28f36460a8e81003378884a5bd
Closes-Bug: #1850916
Signed-off-by: Luke Short <75ade22b5a2100772de069dd66aee23213a7adc0@gmail.com>

openstack/tripleo-common,openstack/tripleo-common