Add support for Etcd v3

[falenn]

Please add support for use with etcd v3.

[falenn]

Looking forward at k8s 1.15+, the ecosystem has migrated to coreos/etcd 3.4+ presenting the new v3 API. As far as I can tell, hpedockerplugin and doryd should follow.

[wdurairaj]

Yes, we can talk to etcd v3 server with the etcd client version shipped with the current docker volume plugin.

If you need exact version of the etcd client (python module) -- this is the information
python-etcd==0.4.5

https://github.com/hpe-storage/python-hpedockerplugin/blob/plugin_v2/requirements-py3.txt#L69
Yes, our source is open source too.

[falenn]

Excellent, my mistake. How are you leveraging the master branch? Is plugin_v2 your master/release branch? Sorry for the confusion