Setting new default for etcd prefix

Change-Id: If0850aa97537512872c7c07243cde0d8445e61d1
diff --git a/libraries/onu_utilities.robot b/libraries/onu_utilities.robot
index e9c4e57..f15ff7e 100755
--- a/libraries/onu_utilities.robot
+++ b/libraries/onu_utilities.robot
@@ -16,7 +16,7 @@
 Documentation     Library for various openonu-go-adpter utilities
 
 *** Variables ***
-${defaultstackname}    minimal
+${defaultstackname}    voltha_voltha
 
 *** Keywords ***
 Calculate Timeout