Fix Sonar complaint about a public mutable Collection

Change-Id: I63c6567228388fcc6ef721c33328b1a35988c3ac
diff --git a/drivers/netconf/src/main/java/org/onosproject/drivers/netconf/TemplateManager.java b/drivers/netconf/src/main/java/org/onosproject/drivers/netconf/TemplateManager.java
index 56a69bb..bd969db 100644
--- a/drivers/netconf/src/main/java/org/onosproject/drivers/netconf/TemplateManager.java
+++ b/drivers/netconf/src/main/java/org/onosproject/drivers/netconf/TemplateManager.java
@@ -47,7 +47,7 @@
     private static final Logger log = getLogger(TemplateManager.class);
     private final Map<String, String> templates = new HashMap<String, String>();
     private TemplateRequestDriver requestDriver;
-    public static final Map<String, Object> EMPTY_TEMPLATE_CONTEXT = new HashMap<String, Object>();
+    private static final Map<String, Object> EMPTY_TEMPLATE_CONTEXT = new HashMap<String, Object>();
 
     /**
      * Internal implementation of the request driver that implements a NETCONF