fix CVE-2019-14697
warn report by quay.io :
https://quay.io/repository/coreos/flannel/manifest/sha256:6d451d92c921f14bfb38196aacb6e506d4593c5b3c9d40a8b8a2506010dc3e10?tab=vulnerabilities
this security issue is not present in 3.11 :
https://github.com/alpinelinux/docker-alpine/issues/34