eam,
Heads up - We are upgrading helm to 2.9.1 (bug fixes only) from 2.8.2 across all the known kubernetes installations (integration, logging, azure), the OOM configuration check, the docs.
Here is the merge order upgrade these in order from 2.8.2 to 2.9.1
0 (merged) - OOM-1299/LOG-320 (logging-analytics/deploy/rancher)
https://gerrit.onap.org/r/#/c/60767/
1 OOM-1299 OOM
https://gerrit.onap.org/r/#/c/60765/
2 OOM-1299 (Integration/deployment/heat/onap-oom)
https://gerrit.onap.org/r/#/c/60785/1
3 https://lf-onap.atlassian.net/browse/INT-626#icft=INT-626 (Integration/deployment)
https://gerrit.onap.org/r/#/c/60907/
4 MSB-221 -ISTIO
https://gerrit.onap.org/r/#/c/58153

What you need to know:
a) When merge 1 for https://gerrit.onap.org/r/#/c/60765/2/kubernetes/onap/Chart.yaml goes in then the tiller version will accept 2.9.1 built helm charts.
b) When you install 2.9.1 as part of an automated install or an manual upgrade of your cluster (only required on the master node) – then a helm upgrade will be required on the server (rancher 1.6.18 installs 2.8.2) – this will then require a restart of your helm repo
See the commands from line 200 to 210 for reference
https://git.onap.org/logging-analytics/tree/deploy/rancher/oom_rancher_setup.sh#n200
sudo helm init --upgrade
sleep 90
echo "verify both versions are the same below"
sudo helm version
echo "start helm server"
sudo helm serve &
echo "add local helm repo"
sudo helm repo add local http://127.0.0.1:8879

You are safe to use Rancher 1.6.18 as this has been tested on the CD system for 6 weeks+
https://git.onap.org/logging-analytics/tree/deploy/rancher/oom_rancher_setup.sh#n57
and the 1.2.10 client on the cluster VMs
https://git.onap.org/logging-analytics/tree/deploy/aws/oom_cluster_host_install.sh#n80