ecscni: unify the plugin add/del method
ecscni: unify the plugin add/del method

kiranmeduri/amazon-ecs-agent,aws/amazon-ecs-agent,swipely/amazon-ecs-agent,swipely/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,aws/amazon-ecs-agent,aws/amazon-ecs-agent,swipely/amazon-ecs-agent,swipely/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,kiranmeduri/amazon-ecs-agent,aws/amazon-ecs-agent