This patch introduces an optional backend encryption for the Ironic API
and Ironic Inspector service. When used in conjunction with enabling
TLS for service API endpoints, network communcation will be encrypted
end to end, from client through HAProxy to the Ironic service.

Change-Id: I3e82c8ec112e53f907e89fea0c8c849072dcf957
Partially-Implements: blueprint add-ssl-internal-network
Depends-On: https://review.opendev.org/#/c/742776/