`CreateChildPrefix` is flaky

[Gerrit91]

Description

https://github.com/metal-stack/metal-apiserver/actions/runs/23789803509/job/69322100766#step:4:902

--- FAIL: Test_networkServiceServer_CreateChildNetwork (21.90s)
    --- FAIL: Test_networkServiceServer_CreateChildNetwork/create_two_child_shared_networks_in_the_different_projects_from_super_network_must_succeed (0.16s)
        repository.go:388: 
            	Error Trace:	/home/runner/work/metal-apiserver/metal-apiserver/pkg/test/repository.go:388
            	            				/home/runner/work/metal-apiserver/metal-apiserver/pkg/service/admin/network/network-service_test.go:480
            	            				/home/runner/work/metal-apiserver/metal-apiserver/pkg/service/admin/network/network-service_test.go:508
            	Error:      	Received unexpected error:
            	            	internal: NotFound prefix 10.100.4.0/22 not found
            	Test:       	Test_networkServiceServer_CreateChildNetwork/create_two_child_shared_networks_in_the_different_projects_from_super_network_must_succeed

[Gerrit91]

This only seems to happen when running together with other tests. Just repeating this one test never fails for me.

It's weird that this can happen because on ListPrefixes the IPAM returns that the prefix is not found. It's this assertion in DeleteNetworks:

		resp, err := testStore.ipam.ListPrefixes(t.Context(), connect.NewRequest(&ipamv1.ListPrefixesRequest{
			Namespace: new(ns),
		}))
		require.NoError(t, err)

[majst01]

This only seems to happen when running together with other tests. Just repeating this one test never fails for me.

It's weird that this can happen because on ListPrefixes the IPAM returns that the prefix is not found. It's this assertion in DeleteNetworks:

  resp, err := testStore.ipam.ListPrefixes(t.Context(), connect.NewRequest(&ipamv1.ListPrefixesRequest{
  	Namespace: new(ns),
  }))
  require.NoError(t, err)

This is a error only the memory backend would return:

func (m *memory) ReadPrefix(_ context.Context, prefix, namespace string) (Prefix, error) {
	m.lock.RLock()
	defer m.lock.RUnlock()
	if _, ok := m.prefixes[namespace]; !ok {
		return Prefix{}, ErrNamespaceDoesNotExist
	}
	result, ok := m.prefixes[namespace][prefix]
	if !ok {
		return Prefix{}, fmt.Errorf("%w prefix %s not found", ErrNotFound, prefix)
	}
	return *result.deepCopy(), nil
}

Still unable to see where this can come from