Make cluster domain configurable for OMEC charts

Also, added chart icon.

Change-Id: I34d806b72fdbad058cab02732b5678900e5f5290
diff --git a/omec/omec-control-plane/values.yaml b/omec/omec-control-plane/values.yaml
index 7f6da5d..21f88f1 100644
--- a/omec/omec-control-plane/values.yaml
+++ b/omec/omec-control-plane/values.yaml
@@ -86,6 +86,7 @@
     #  cpu: 2
 
 config:
+  clusterDomain: cluster.local
   hss:
     hssdb: cassandra
     s6a: