server: use buffered channel to avoid goroutine leak (#11941)
server: use buffered channel to avoid goroutine leak (#11941)

Signed-off-by: Gaurav Singh <8968a526fc7a1cdc1e19b8d2aa18b75f407d6450@gmail.com>
ajityagaty/etcd,mqliang/etcd,etcd-io/etcd,li-ang/etcd,mqliang/etcd,rnaveiras/etcd,etcd-io/etcd,mkumatag/etcd,li-ang/etcd,gyuho/etcd,coreos/etcd,coreos/etcd,ajityagaty/etcd,etcd-io/etcd,ajityagaty/etcd,gyuho/etcd,mkumatag/etcd,rnaveiras/etcd,rnaveiras/etcd,mqliang/etcd,mkumatag/etcd