Extended serial function for work with maps too

Change-Id: I06fba168293ab71981868a8fa75ad1cee14040bf
diff --git a/src/com/mirantis/mk/Common.groovy b/src/com/mirantis/mk/Common.groovy
index b31f40d..ed3f4db 100644
--- a/src/com/mirantis/mk/Common.groovy
+++ b/src/com/mirantis/mk/Common.groovy
@@ -215,7 +215,7 @@
         def step = stepsArray[i]
         def dummySteps = [:]
         def stepKey
-        if(step[1] instanceof Iterable){
+        if(step[1] instanceof List || step[1] instanceof Map){
             for(j=0;j < step[1].size; j++){
                 if(step[1] instanceof List){
                     stepKey = j