Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Add a label which prevents a node from being added to a cloud load balancer

There are a variety of reasons that you may not want a node in a cluster to participate in a cloud load balancer. For example workload isolation for security, or managing network throughput, or because the node is not in the appropriate virtual network (cluster's that span environments)

This PR adds a label so that you can select which nodes you want to participate.