Using kind-voltha 6.0.0 for 2.6 based jobs (master has issues in setting the log level on older releases)

Change-Id: I315ae80773e5986c9e7495d572f553dfb0e83e0c
diff --git a/jjb/pipeline/voltha-scale-test-2.6.groovy b/jjb/pipeline/voltha-scale-test-2.6.groovy
index db5107e..32ba833 100644
--- a/jjb/pipeline/voltha-scale-test-2.6.groovy
+++ b/jjb/pipeline/voltha-scale-test-2.6.groovy
@@ -118,7 +118,7 @@
           userRemoteConfigs: [[
             url: "https://gerrit.opencord.org/kind-voltha",
           ]],
-          branches: [[ name: "master", ]],
+          branches: [[name: 'refs/tags/6.0.0']],
           extensions: [
             [$class: 'WipeWorkspace'],
             [$class: 'RelativeTargetDirectory', relativeTargetDir: "kind-voltha"],