don't close the client event listeners until the context is closed
don't close the client event listeners until the context is closed

ctx.Close() will close the upstream of the clients, so event listeners
(and Fanout) are closed in consequence.

So that all the event listeners can listen all the event until end.

Signed-off-by: Lai Jiangshan <b337eedf453972390e4695e362aeea2634ef4e0c@gmail.com>

hyperhq/runv,jinfenw/runv,laijs/runv,bergwolf/runv,gao-feng/runv,laijs/runv,wrouesnel/runv,gao-feng/runv,jinfenw/runv,feiskyer/runv,laijs/runv,bergwolf/runv,gnawux/runv,hyperhq/runv,bergwolf/runv,YaoZengzeng/runv,feiskyer/runv,gnawux/runv,gnawux/runv,wrouesnel/runv,YaoZengzeng/runv,jinfenw/runv,gao-feng/runv,hyperhq/runv