agent/acs/acs_handler.go: Reduce the heartbeat timeout to 1 minute
agent/acs/acs_handler.go: Reduce the heartbeat timeout to 1 minute

    This will reduce the acs disconnection period, the maximum
    disconnection period of acs would be 2 minutes before agent
    try to connect to acs again.

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