[Upgrade] Add check for cluster name availability

Add check for cluster_name var that it's present, otherwise operator
should check pillar data for salt master node.

Change-Id: Ib7174d1058a040101b9d6c6a260d6f7a6075446e
Related-Prod: PROD-29600 (PROD:29600)
diff --git a/upgrade-mcp-release.groovy b/upgrade-mcp-release.groovy
index 161029e..8e5bcdc 100644
--- a/upgrade-mcp-release.groovy
+++ b/upgrade-mcp-release.groovy
@@ -288,6 +288,10 @@
             }
             python.setupPepperVirtualenv(venvPepper, saltMastURL, saltMastCreds)
             def minions = salt.getMinions(venvPepper, '*')
+            def cluster_name = salt.getPillar(venvPepper, 'I@salt:master', "_param:cluster_name").get("return")[0].values()[0]
+            if (cluster_name == '' || cluster_name == 'null' || cluster_name == null) {
+                error('Pillar data is broken for Salt master node! Please check it manually and re-run pipeline.')
+            }
 
             stage('Update Reclass and Salt-Formulas') {
                 common.infoMsg('Perform: Full salt sync')
@@ -298,7 +302,6 @@
                 common.infoMsg('Perform: archiveReclassInventory before upgrade')
                 archiveReclassInventory(inventoryBeforeFilename)
 
-                def cluster_name = salt.getPillar(venvPepper, 'I@salt:master', '_param:cluster_name').get('return')[0].values()[0]
                 try {
                     salt.cmdRun(venvPepper, 'I@salt:master', 'cd /srv/salt/reclass/ && git status && git diff-index --quiet HEAD --')
                 }