fix(kuma-cp): memory store keeps children after owner update

[jakubdyszkiewicz]

Memory store was not keeping children after owner update.
Production is not affected, because memory store is not used on prod, only in tests and local development.
This Postgres and K8S is NOT affected.

That was the real cause of flaky update policy on KDS.
Default mesh resources created by tr-test mesh (TrafficRoute suite) were there after the test was done.
Then Global CP was syncing them down to Zone CP and Zone CP was rejecting all TrafficRoute resources because mesh was absent.

2022-11-24T13:30:04.268Z	INFO	kds-zone	creating a new resource from upstream	{"type": "CircuitBreaker", "name": "circuit-breaker-all-tr-test", "mesh": "tr-test"}
2022-11-24T13:30:04.270Z	INFO	kds-zone	error during callback received, sending NACK	{"peer-id": "global", "err": "failed to create k8s resource: admission webhook \"owner-reference.kuma-admission.kuma.io\" denied the request: Mesh.kuma.io \"tr-test\" not found", "errVerbose": "admission webhook \"owner-reference.kuma-admission.kuma.io\" denied the request: Mesh.kuma.io \"tr-test\" not found\nfailed to create k8s resource\ngh.neting.cc/kumahq/kuma/pkg/plugins/resources/k8s.(*KubernetesStore).Create\n\t/home/circleci/project/pkg/plugins/resources/k8s/store.go:75\ngh.neting.cc/kumahq/kuma/pkg/core/resources/store.(*paginationStore).Create\n\t/home/circleci/project/pkg/core/resources/store/pagination_store.go:30\ngh.neting.cc/kumahq/kuma/pkg/metrics/store.(*MeteredStore).Create\n\t/home/circleci/project/pkg/metrics/store/store.go:38\ngh.neting.cc/kumahq/kuma/pkg/core/resources/store.(*customizableResourceStore).Create\n\t/home/circleci/project/pkg/core/resources/store/customizable_store.go:30\ngh.neting.cc/kumahq/kuma/pkg/kds/store.(*syncResourceStore).Sync\n\t/home/circleci/project/pkg/kds/store/sync.go:152\ngh.neting.cc/kumahq/kuma/pkg/kds/zone.Callbacks.func1\n\t/home/circleci/project/pkg/kds/zone/components.go:145\ngh.neting.cc/kumahq/kuma/pkg/kds/client.(*kdsSink).Receive\n\t/home/circleci/project/pkg/kds/client/sink.go:64\ngh.neting.cc/kumahq/kuma/pkg/kds/zone.Setup.func1.2\n\t/home/circleci/project/pkg/kds/zone/components.go:76\nruntime.goexit\n\t/home/circleci/go/src/runtime/asm_amd64.s:1571"}

Checklist prior to review

• Link to docs PR or issue --
• Link to UI issue or PR --
• Is the issue worked on linked? --
• The PR does not hardcode values that might break projects that depend on kuma (e.g. "kumahq" as a image registry) --
• The PR will work for both Linux and Windows, system specific functions like syscall.Mkfifo have equivalent implementation on the other OS --
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• Manual Kubernetes Tests --
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