CI: Check in new PR if scripts have warnings/suggestions

[dougsland]

Issue

• Please create make shellcheck or similar command to check all shell scripts in the source tree if there are warnings or suggestions (and fix it :+1: : ).
• Every new PR (if it's related to shell scripting) should check if the change includes warnings and suggestions and give negative review so the author must fix it before the merge.

Example of warning in existing shell scripts:

#sig-windows-dev-tools/sync# shellcheck linux/controlplane.sh 

In linux/controlplane.sh line 1:
: '
^-- SC2148: Tips depend on target shell and yours is unknown. Add a shebang.

In linux/controlplane.sh line 35:
k8s_linux_registry=${2}
^----------------^ SC2034: k8s_linux_registry appears unused. Verify use (or export if used externally).

In linux/controlplane.sh line 40:
echo "Using $kubernetes_version as the Kubernetes version"
            ^-----------------^ SC2154: kubernetes_version is referenced but not assigned.

In linux/controlplane.sh line 41:
echo "Overwriting bins is set to '$overwrite_bins'"
                                  ^-------------^ SC2154: overwrite_bins is referenced but not assigned.

In linux/controlplane.sh line 75:
kubelet=${k8s_linux_kubelet_deb}-00 \
        ^----------------------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
kubelet="${k8s_linux_kubelet_deb}"-00 \

In linux/controlplane.sh line 76:
kubeadm=${k8s_linux_kubelet_deb}-00 \
        ^----------------------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
kubeadm="${k8s_linux_kubelet_deb}"-00 \

In linux/controlplane.sh line 77:
kubectl=${k8s_linux_kubelet_deb}-00
        ^----------------------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
kubectl="${k8s_linux_kubelet_deb}"-00

In linux/controlplane.sh line 144:
mkdir -p $HOME/.kube
         ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
mkdir -p "$HOME"/.kube

In linux/controlplane.sh line 145:
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
                                      ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
sudo cp -i /etc/kubernetes/admin.conf "$HOME"/.kube/config

In linux/controlplane.sh line 146:
sudo chown $(id -u):$(id -g) $HOME/.kube/config
           ^------^ SC2046: Quote this to prevent word splitting.
                    ^------^ SC2046: Quote this to prevent word splitting.
                             ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
sudo chown $(id -u):$(id -g) "$HOME"/.kube/config

In linux/controlplane.sh line 149:
cp $HOME/.kube/config /var/sync/shared/config
   ^---^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
cp "$HOME"/.kube/config /var/sync/shared/config

More info: https://github.com/koalaman/shellcheck

[dougsland]

/good-first-issue

[k8s-ci-robot]

@dougsland: This request has been marked as suitable for new contributors.

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In response to [this](https://github.com/kubernetes-sigs/sig-windows-dev-tools/issues/163): >/good-first-issue Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.