manager: consistent cleanup of grpc servers and listeners
manager: consistent cleanup of grpc servers and listeners

server.Stop closes underlying listeners

Signed-off-by: Alexander Morozov <2043cda4df124b840b98ee1c4307c199042efdf7@gmail.com>

vasil-yordanov/swarmkit,Noyan759/swarmkit,AliyunContainerService/swarmkit,Noyan759/swarmkit,yongtang/swarmkit,docker/swarmkit,diogomonica/swarmkit,diogomonica/swarmkit,jlhawn/swarmkit,AliyunContainerService/swarmkit,allencloud/swarmkit,vasil-yordanov/swarmkit,allencloud/swarmkit,alyyousuf7/swarmkit,elifa/swarmkit,jlhawn/swarmkit,yongtang/swarmkit,RenaudWasTaken/swarmkit,sungwonh/swarmkit,cezarsa/swarmkit,cheyang/swarmkit,cheyang/swarmkit,aaronlehmann/swarmkit,alyyousuf7/swarmkit,RenaudWasTaken/swarmkit,fate-grand-order/swarmkit,dperny/swarmkit-1,cezarsa/swarmkit,dperny/swarmkit-1,sungwonh/swarmkit,elifa/swarmkit,fate-grand-order/swarmkit,deljuven/swarmkit,docker/swarmkit,deljuven/swarmkit,aaronlehmann/swarmkit