Per the documentation, , it shows that I should be able to change the docker engine version via the command

sudo ros engine enable

which works to change the engine on the worker node running Rancher OS v.1.5.3, but after doing so, the node becomes unavailable in the cluster with the error

Kubelet stopped posting node status

I found a known issue (https://github.com/rancher/os/issues/2710) with trying to set the docker engine when provisioning but trying to determine how to get around this.