Fix JSON parsing

Change-Id: I22a50eb4fb9089bf9f70e6060363b9e080e65afb
diff --git a/src/com/mirantis/mk/Common.groovy b/src/com/mirantis/mk/Common.groovy
index 12e3443..1789bd7 100644
--- a/src/com/mirantis/mk/Common.groovy
+++ b/src/com/mirantis/mk/Common.groovy
@@ -405,7 +405,7 @@
  */
 def parseJSON(jsonString){
    def m = [:]
-   def lazyMap = new JsonSlurper().parseText(output)
+   def lazyMap = new JsonSlurper().parseText(jsonString)
    m.putAll(lazyMap)
    return m
 }