Add nodeSelector to prevent scheduled pods on Windows worker nodes

[hugoprudente]

It's becoming common the multi OS worker nodes on the EKS.

When deployment the DaemonSet as no nodeSelector is added the pods will try to be scheduled on Windows nodes and fail.

Solution idea, is to add the node selector to based on the Operational System with

      nodeSelector:
        beta.kubernetes.io/os: linux   

[andyjcooperuk]

I also have this requirement - Currently you cannot schedule the required pods on windows nodes as the fluentd-cloudwatch image is a debian image and there isn't a Windows version yet - We have raised this with AWS but it would be good to be-able to exclude Windows nodes for now using the node selector

[hugoprudente]

Thanks @andyjcooperuk for the PR, I hope this get merged soon!