E2e: Unhold CI packages before installing

It is common to mark kubeadm and related packages as held at a specific
version to avoid accidental upgrades. The script for injecting CI
artifacts does not take this into account, which means that if the base
image used already has some version of a package installed and held, the
script will fail to install the asked for version.
To avoid this, we unhold before installing the packages and then hold
again, as customary. Holding after installation also avoids any
unintended upgrades later.

Author: lentzi90

test/framework/kubernetesversions/data/debian_injection_script.envsubst.sh.tpl

@@ -88,7 +88,9 @@ if [[ "$${KUBERNETES_VERSION}" != "" ]]; then
     PACKAGE_VERSION="$(apt-cache madison kubelet | grep "$${VERSION_REGEX}-" | head -n1 | cut -d '|' -f 2 | tr -d '[:space:]')"
     for CI_PACKAGE in "$${PACKAGES_TO_TEST[@]}"; do
       echo "* installing package: $${CI_PACKAGE} $${PACKAGE_VERSION}"
+      apt-mark unhold "$${CI_PACKAGE}"
       apt-get install -y "$${CI_PACKAGE}=$${PACKAGE_VERSION}"
+      apt-mark hold "$${CI_PACKAGE}"
     done
   else
     CI_URL="https://dl.k8s.io/ci/$${KUBERNETES_VERSION}/bin/linux/amd64"