[CFT cyperf agent] 2 subnets for 1 security group  #8

In the file deployment/aws/cloudformation/controller_and_agent_pair/cyperf_controller_and_agent_pair_existing_vpc.json it seems that we cannot use 2 different subnets (1 for management, 1 for test) for Cyperf Agents because the Security Group assigned to the agent is assigned to both interfaces.
From a AWS point of view, I don't know if it is possible to have multiple subnets for the same SG, but from a Cyperf point of view, we could wish to separate mgmt security group and test security group for our agents.