Add option to store UUID

[magicalyak]

in the agent.conf, you need to set store_UUID = True for persistence to work on a container or demo environment (where the underlying instance might be swapped but you want it to report the same on the controller). We should add a variable to set this to true. This solves that issue.

Current my workaround is this
sudo sed -i.bak 's/store_uuid = False/store_uuid = True/' /etc/controller-agent/agent.conf

[brianehlert]

just added this as default behavior whenever nginx_controller_hostname or nginx_controller_instance_name is defined.

With the expectation that if those are not defined and thus get written to the agent.conf via the installer, the hostname might change.

Instance_name will always remain fixed and is set at installation.
However, nginx_controller_hostname could safely change.