ci: k8s: Export KUBERNETES env var

So we have a better control on which flavour of kubernetes kata-deploy
is expected to be targetting.

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

.github/workflows/run-k8s-tests-on-aks.yaml

@@ -40,6 +40,7 @@ jobs:
       GH_PR_NUMBER: ${{ inputs.pr-number }}
       KATA_HOST_OS: ${{ matrix.host_os }}
       KATA_HYPERVISOR: ${{ matrix.vmm }}
+      KUBERNETES: "vanilla"
       USING_NFD: "false"
     steps:
       - uses: actions/checkout@v3

.github/workflows/run-k8s-tests-on-sev.yaml

@@ -33,6 +33,7 @@ jobs:
       PR_NUMBER: ${{ inputs.pr-number }}
       KATA_HYPERVISOR: ${{ matrix.vmm }}
       KUBECONFIG: /home/kata/.kube/config
+      KUBERNETES: "vanilla"
       USING_NFD: "false"
     steps:
       - uses: actions/checkout@v3

.github/workflows/run-k8s-tests-on-snp.yaml

@@ -33,6 +33,7 @@ jobs:
       PR_NUMBER: ${{ inputs.pr-number }}
       KATA_HYPERVISOR: ${{ matrix.vmm }}
       KUBECONFIG: /home/kata/.kube/config
+      KUBERNETES: "vanilla"
       USING_NFD: "false"
     steps:
       - uses: actions/checkout@v3

.github/workflows/run-k8s-tests-on-tdx.yaml

@@ -32,6 +32,7 @@ jobs:
       DOCKER_TAG: ${{ inputs.tag }}
       PR_NUMBER: ${{ inputs.pr-number }}
       KATA_HYPERVISOR: ${{ matrix.vmm }}
+      KUBERNETES: "k3s"
       USING_NFD: "true"
     steps:
       - uses: actions/checkout@v3