The proxy scheduler implemented its own timer state machine. It's
simpler and more efficient to leverage the Go runtime's timer heap by
using time.AfterFunc.
This commit adds a time.Timer to each scheduler entry, and starts and
stops those timers as necessary. Then the mainloop goroutine and its
associated logic are not needed.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
c56e8c2533