kyverno-policies(kube): exclude longhorn instance-manager pods from cpu stripping

The longhorn instance-manager and engine-image pods carry
longhorn.io/component labels, not app, so the exclusions never matched.
Kyverno stripped their cpu requests at admission, longhorn-manager saw a
spec mismatch and deleted the pod in a loop, and after any node reboot
all longhorn volumes stayed detached with every workload stuck in
ContainerCreating. Match the real labels instead.

kubernetes/system/kyverno-policies/policy-strip-cpu-requests.yaml

@@ -80,13 +80,13 @@ spec:
                 - longhorn-system
               selector:
                 matchLabels:
-                  app: instance-manager
+                  longhorn.io/component: instance-manager
           - resources:
               namespaces:
                 - longhorn-system
               selector:
                 matchLabels:
-                  app: engine-image
+                  longhorn.io/component: engine-image
       mutate:
         # `request.object` is available in BOTH admission and background modes:
         # the backgroundController synthesizes an admission-like request for