This patch adds a configurable option for deployers to apply security
hardening by adjusting apply_security_hardening to true within
the user_variables.yml file. In addition, security hardening is enabled
on AIO builds by default.
Documentation about the security role and how to enable it are also included
in this patch.
Implements: blueprint security-hardening
Change-Id: Ic05ab7eacd6a1966814764b8290817fb78732758
411c51c8d1