Run tests on newer k8s versions and improve tests

[dennisme]

In #17 we noticed that we had forgotten to run make kube-gen which resulted in the following error an apply:

declared in schema .spec.slos[8].infoLabels: field not declared in schema .spec.slos[9].infoLabels: field not declared in schema

The tests could run the gen and error if any files are changed. Also the k8s integration tests could be updated to apply a example slo which would have also caught that.