In some environments, additional volumes are rqeuired for the apiserver
to function as expected. For example, on CentOS 7 controller nodes, the
host CA certificate bundles mounted at /etc/ssl/certs are broken since
this directory contains symlinks pointing to an unmounted path.

In other environments this may be used to provision a specific directory
which is referred to by other apiserver arugments, e.g.
"--oidc-ca-file".

Allow mounting extra volumes to apiserver pod

* Fix syntax a bit

* Change and update documentation a bit

* Rename `cni_version` to `cni_package_version` same way as `kubernetes_package_version`.

* Parametrize cni package name.

* Parametrize docker package name.

* Fix `docker_package_name` and `cni_package_name` variables.

* Update unit test because of parametrized docker cni package names.

* Update documentation and unit test because of `cni_package_version` change.

* Parametrize version of docker package to install and pin package for Debian/Ubuntu.

* Updated documentation

* Rename `cni_package_version` variable back to `cni_version` for back compatibility.

* `$docker_package_version` name typo fix

* Rename `docker_package_pin` variable to `package_pin`.

* Pin kube* packages

* Pin kubernetes-cni package

* Cover with unit tests

* Fix `docker_version`

So updating docs to match

README.md was still pointing at an old version.