appveyor: exclude vendor directory when running tests
appveyor: exclude vendor directory when running tests

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