Allow --pause-image to set docker sandbox image also

Cleanup --flannel-backend help text

Upgrade go to 1.13.5

Mutable --node-label values for server/agent sub-commands.

For #577

Update README.md: k3s does not exclude legacy/alpha/non-default features anymore

Values passed in via the server/agent `--node-label` flag are treated as mutable. They are passed through to the kubelet just as before but after the kubelet comes up they are applied again. This allows for passing labels a k3s start-time that may be necessary for scheduling but may change from boot to boot, e.g. `k3os.io/version` after an upgrade.

Tested locallon on my amd64 workstation with the docker container.

Addresses #1119.

In the past, yes k3s did exclude all those legacy, alpha, non-default
features from Kubernetes source as you can see in
https://github.com/rancher/k3s/pull/113. But not anymore.

As you can see in the source code, most of legacy/alpha/non-default
features is available in k3s, and misleading README should be updated.

But please, don't get me wrong. I'm actually glad to see those features
enabled in k3s. :)

Reference:
  https://github.com/kubernetes/kubernetes/compare/v1.16.3...rancher:v1.16.3-k3s.1

Code cleanup

Bump dqlite to support arm 32-bit

Performance tests with clusterloader2

Update Docker Compose file to use v1.0.0 image versions

Verify selinux status before downloading

Bump Traefik to 1.7.19

Update base pause image to rancher repo

Signed-off-by: dduportal <1522731+dduportal@users.noreply.github.com>

initial loadtesting framework

Bump kine/k8s to fix broken label based pagination