etcd cluster chart and usage in voltha requirements

Addition of a chart dedicated to creating etcdCluster CRD instances from an already installed etcd-operator
This is good for specifying custom etcd images, retention periods, and custom repo locations.
Also helpful in installing instances of an etcdCluster separate from installing etcd-operator

Modify the voltha chart to require the etcd-cluster chart rather than etcd-operator, given the etcd instance is whats truly required.
This allows the upgrade/removal of voltha to take its etcd-cluster with it, without removing etcd-operator.

Update the voltha chart to make the inclusion of freeradius optional and remove unused consul config references.

Tested by running:
helm install -n cord-kafka incubator/kafka --set persistence.enabled=false --set zookeeper.persistence.enabled=false
helm install -n etcd-operator stable/etcd-operator

  wait for etcdclusters CRD to be created...

helm dep update ~/source/helm-charts/voltha
helm install -n voltha ~/source/helm-charts/voltha

Change-Id: I7001943d74fdbd38f4d786982c70908ba24fd0ca
diff --git a/voltha/templates/_helpers.tpl b/voltha/templates/_helpers.tpl
index d2d876f..44b0103 100644
--- a/voltha/templates/_helpers.tpl
+++ b/voltha/templates/_helpers.tpl
@@ -16,7 +16,7 @@
 
 {{- define "voltha-vcore.cmd" }}
 - "voltha/voltha/main.py"
-- "--etcd=etcd-cluster.default.svc.cluster.local:2379"
+- "--etcd={{ .Values.etcdReleaseName }}.default.svc.cluster.local:2379"
 - "--kafka={{ .Values.kafkaReleaseName }}.default.svc.cluster.local"
 - "--rest-port=8880"
 - "--grpc-port=50556"