Add tolerations and nodeSelector to seldon-core-operator helm chart

[yavorivanov-cw]

We are currently using seldon-core-operator and would like to add tolerations and nodeSelector to the seldon-controller-manager.

We are using the chart like this:

helm upgrade --install seldon-core seldon-core-operator \
   --repo https://storage.googleapis.com/seldon-charts \
   --set usageMetrics.enabled=false \
   --set istio.enabled=false \
   --create-namespace \
   --namespace seldon-system