Operator bgpv2 Test_NodeLabels is flaky

[bimmlerd]

To repro locally:

0. Install stress via go install golang.org/x/tools/cmd/stress@latest
1. go test -c -race ./operator/pkg/bgpv2 && stress ./bgpv2.test -test.run=Test_NodeLabels

It's possible that other bgpv2 tests are also flaky, but this one gives the strongest signal: For me, this results in 1m0s: 152 runs so far, 24 failures (15.79%)

The cause is likely to be the usage of real informers against the fake K8s clientset. See https://github.com/kubernetes/client-go/blob/04ef61f72b7bc5ae6efef4e4dc0001746637fdb3/examples/fake-client/main_test.go#L74-L81 for an inspiration on how to fix this.