Fix etcd image version

Change-Id: If4cf66bee72dfa9b9d2007b85e0f31ce3067132f
diff --git a/etcd-cluster/values.yaml b/etcd-cluster/values.yaml
index 764c7e8..ac3ae31 100644
--- a/etcd-cluster/values.yaml
+++ b/etcd-cluster/values.yaml
@@ -24,7 +24,7 @@
 images:
   etcd:
     repository: "quay.io/coreos/etcd"
-    tag: "3.2.18"
+    tag: "v3.2.18"
   busybox:
     repository: "busybox"
     tag: "1.28.1-glibc"