k8s driver: add user defined node selector

[sgotti]

Add a node selector option to the k8s driver so the k8s scheduler will schedule pods only on k8s nodes matching this selector (the k8s driver already adds a node selector to filter by node architecture: kubernetes.io/arch or beta.kubernetes.io/arch on old k8s version)

[starkers]

Yes this is very desirable, another thing I've identified (as important to have) would be an adjustable memory request limit.. that way users can carve out enough RAM to do the operations they need safely and with the guarantees of kubernetes auto-scaling..

I'm about 5 minutes new to the codebase and a week into my first agola deploy but I'm very happy to have a crack at it these.. where would you think is a good place to configure such (optional) tweaks?

BTW, agola is very nice!

[Dan6erbond]

I have a question related to this - does Agola allow users to specify in their CI templates which arch to be running on? I would like to build Docker images for AMD64 and ARM and couldn't find any relevant docs. Thanks!