Calico: fixup check when ipipMode / vxlanMode is not present (#7195)

calicoctl.sh get ipPool default-pool -o json
{
  "kind": "IPPool",
  "apiVersion": "projectcalico.org/v3",
  "metadata": {
    "name": "default-pool",
...
  },
  "spec": {
    "cidr": "10.233.64.0/18",
    "ipipMode": "Always",
    "natOutgoing": true,
    "blockSize": 24,
    "nodeSelector": "all()"
  }
}

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>