Update cilium_ipsec_enabled check (#7413)

When attempting a fresh install without cilium_ipsec_enabled I ran
into the following error:

failed: [k8m01] (item={'name': 'cilium', 'file': 'cilium-secret.yml', 'type': 'secret', 'when': 'cilium_ipsec_enabled'}) =>
{"ansible_loop_var": "item", "changed": false, "item": {"file": "cilium-secret.yml", "name": "cilium", "type": "secret",
"when": "cilium_ipsec_enabled"},"msg": "AnsibleUndefinedVariable: 'cilium_ipsec_key' is undefined"}

Moving the when condition from the item level to the task level solved
the issue.