Handle event monitor errors at engine.go
Handle event monitor errors at engine.go

Signed-off-by: Dong Chen <252dc6b7229d6040aded2d6fd307bed15f92f3c6@docker.com>

allencloud/swarm,fugr/swarm,jimmycmh/swarm,jimmycmh/swarm,allencloud/swarm,fugr/swarm