The delegate file size is zero after restart VM

[issssu]

The flannel runs properly until the VM was restarted, the pod could not delete normally.
We checked the delegate file created by the flannel: /var/lib/cni/flannel/43bd9329948d3095ru40323009fd9s00erer0dd00s9edfad9edss0y9999se9de, found that the file size is 0.
Maybe we can add the sync function in saveScratchNetConf(containerID, dataDir string, netconf []byte), refer to the etcd's code ioutil.WriteAndSyncFile, thanks.

# ls -l /var/lib/cni/flannel
-rw------- 1 root root 238 Jun 8 22:11 f913be9f5cd806f8ac8801f6b6abf51865783be347b3d3f66b0010fc922a06c6
-rw------- 1 root root 0 Jun 12 16:12 43bd9329948d3095ru40323009fd9s00erer0dd00s9edfad9edss0y9999se9de

[manuelbuil]

Makes sense, we'll try to do it in the next weeks

[manuelbuil]

Merged