A watcher would output the current progress item when it was detached,
in case it missed that item earlier, which would leave the user seeing
some intermediate step of the operation. This commit changes it to only
output it on detach if it didn't already output the same item.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
Upstream-commit: fde2329eaa1fab2327ae2e775af5aa04e2726ed5
Component: engine