This patch adds a number of configration options and playbook variables
that govern SSL validation and authentication when accessing the image
store to download the image and configdrive from the deploy ramdisk.
Most of them are not yet used in the default set of playbooks provided
with the driver
(for example some of them require yet unreleased Ansible 2.4),
however they can be used by custom playbooks, for example to upload
and enable those custom CA bundle and cert files to the ramdisk at
deploy time.
This patch also sets DevStack to disable validation of image store SSL
certificate by ansible deploy interface (similar to how IPA is currently
confugured).
This patch also caps Anisble < 2.4, since our custom callback plugin
has troubles with the newest Ansible 2.4 version (to be fixed later).
Change-Id: Id40f1067361cc32e98973c70fc5cd3d4242308d0
Closes-Bug: #1717858
0cdc53948f