Update CNI plugins and cri-tools for kubeadm docs

We now bump the used CNI plugins version to v1.1.1 and cri-tools to
v1.25.0. I also reworked the scripts to be more consistent when it comes
to using double quotes.

Signed-off-by: Sascha Grunert <sgrunert@redhat.com>

content/en/docs/setup/production-environment/tools/kubeadm/install-kubeadm.md

@@ -212,28 +212,29 @@ sudo systemctl enable --now kubelet
 Install CNI plugins (required for most pod network):
 
 ```bash
-CNI_VERSION="v0.8.2"
+CNI_PLUGINS_VERSION="v1.1.1"
 ARCH="amd64"
-sudo mkdir -p /opt/cni/bin
-curl -L "https://github.com/containernetworking/plugins/releases/download/${CNI_VERSION}/cni-plugins-linux-${ARCH}-${CNI_VERSION}.tgz" | sudo tar -C /opt/cni/bin -xz
+DEST="/opt/cni/bin"
+sudo mkdir -p "$DEST"
+curl -L "https://github.com/containernetworking/plugins/releases/download/${CNI_PLUGINS_VERSION}/cni-plugins-linux-${ARCH}-${CNI_PLUGINS_VERSION}.tgz" | sudo tar -C "$DEST" -xz
 ```
 
 Define the directory to download command files
 
 {{< note >}}
 The `DOWNLOAD_DIR` variable must be set to a writable directory.
-If you are running Flatcar Container Linux, set `DOWNLOAD_DIR=/opt/bin`.
+If you are running Flatcar Container Linux, set `DOWNLOAD_DIR="/opt/bin"`.
 {{< /note >}}
 
 ```bash
-DOWNLOAD_DIR=/usr/local/bin
-sudo mkdir -p $DOWNLOAD_DIR
+DOWNLOAD_DIR="/usr/local/bin"
+sudo mkdir -p "$DOWNLOAD_DIR"
 ```
 
 Install crictl (required for kubeadm / Kubelet Container Runtime Interface (CRI))
 
 ```bash
-CRICTL_VERSION="v1.22.0"
+CRICTL_VERSION="v1.25.0"
 ARCH="amd64"
 curl -L "https://github.com/kubernetes-sigs/cri-tools/releases/download/${CRICTL_VERSION}/crictl-${CRICTL_VERSION}-linux-${ARCH}.tar.gz" | sudo tar -C $DOWNLOAD_DIR -xz
 ```