Memberships: Use external volume, remove one from the Helm chart.

Change-Id: Ie2afcd9ab28a12e7d6bea6375a96e00a0f63b525
diff --git a/charts/memberships/values.yaml b/charts/memberships/values.yaml
index c4be0f8..7dab384 100644
--- a/charts/memberships/values.yaml
+++ b/charts/memberships/values.yaml
@@ -2,6 +2,5 @@
   repository: giolekva/memberships
   tag: latest
   pullPolicy: Always
-storage:
-  size: 1Gi
+volumeClaimName: "data"
 portName: http