TCS: Fix memleak by escaping ticker loop
TCS: Fix memleak by escaping ticker loop

Prior to this change, the publishTicker loop would run forever, leaking
a Goroutine per run because a ticker's 'Stop' function doesn't close the
channel.

This adds an additional channel to cancel it which should let it reclaim
all memory.

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