ICSHWI-7061 Interpret iocs_to_deploy as a CSV

When specifying extra variables to a playbook only strings are supported so we have to accept a string of comma separated IOCs and convert it to a 'proper' list.

• If iocs_to_deploy is not specified then all IOCs in the inventory will be considered for deployment.
• If iocs_to_deploy is an empty string then no IOC will be deployed.