testing/k3s: security fixes CVE-2020-8555 and CVE-2020-10749

- Upgrade to 1.18.3.1
- Ref https://github.com/rancher/k3s/releases
7 jobs for !8704 with k3s in 7 minutes and 18 seconds
detached
Status Job ID Name Coverage
  Lint
passed #132024
docker-alpine x86_64
lint

00:00:24

 
  Build
passed #132029
docker-alpine ci-build aarch64
build-aarch64

00:04:42

passed #132030
docker-alpine ci-build armv7
build-armv7

00:06:11

passed #132028
docker-alpine ci-build ppc64le
build-ppc64le

00:06:52

passed #132027
docker-alpine ci-build s390x
build-s390x

00:03:09

passed #132026
docker-alpine ci-build x86
build-x86

00:03:18

passed #132025
docker-alpine ci-build x86_64
build-x86_64

00:02:59