authelia: Add startup probe

I am not entirely sure why, but it seems like the Kubelet *always*
misses the first check in the readiness probe.  This causes a full
60-second delay before the Authelia pod is marked as "ready," even
though it was actually ready within a second of the container starting.

To avoid this very long delay, during which Authelia is unreachable,
even though it is working fine, we can add a startup probe with a much
shorter check interval.  The kubelet will not start readiness probes
until the startup probe returns successfully, so it won't miss the first
one any more.

authelia/authelia.yaml

@@ -81,13 +81,21 @@ spec:
           value: /run/authelia/secrets/session.secret
         - name: AUTHELIA_STORAGE_ENCRYPTION_KEY_FILE
           value: /run/authelia/secrets/storage.encryption_key
+        startupProbe:
+          httpGet:
+            port: 9091
+            path: /api/health
+          failureThreshold: 30
+          periodSeconds: 3
+          initialDelaySeconds: 5
+          successThreshold: 1
+          timeoutSeconds: 1
         readinessProbe:
           httpGet:
             port: 9091
             path: /api/health
           failureThreshold: 3
           periodSeconds: 60
-          initialDelaySeconds: 5
           successThreshold: 1
           timeoutSeconds: 1
         volumeMounts: