mkcloud: add documentation about ha setups and internal variables
mkcloud: add documentation about ha setups and internal variables

gosipyan/automation,SUSE-Cloud/automation,vmoravec/automation,gosipyan/automation,aspiers/automation,gosipyan/automation,gosipyan/automation,SUSE-Cloud/automation,vmoravec/automation,vmoravec/automation,aspiers/automation,SUSE-Cloud/automation,aspiers/automation,vmoravec/automation,aspiers/automation,SUSE-Cloud/automation