Kubernetes upgrade from 1.5 -> 1.6 requires a configmap to be created in the kube-system namespace to minimize downtime. If kubectl -n kube-system get configmap kube-dns does not already have a configmap, BEFORE upgrade you can execute kubectl create configmap -n kube-system kube-dns.
Kubernetes changed taints from an annotation in 1.5, to a field in 1.6. Editing the taints by hand is a workaround for any issues. See: #2594
Some Kubernetes upgrades from 1.6.x -> 1.6.x have experience issues with secrets and service accounts. Deleting the secrets have been a workaround (not validated). See: #2576