Install older bundler version in kitchen test

Change-Id: Iae2dee3a2010a3af1f7c271dbdbe296234d4bada
diff --git a/src/com/mirantis/mk/Ruby.groovy b/src/com/mirantis/mk/Ruby.groovy
index 3c96b29..f9df3ad 100644
--- a/src/com/mirantis/mk/Ruby.groovy
+++ b/src/com/mirantis/mk/Ruby.groovy
@@ -21,7 +21,7 @@
  * Install kitchen tools
  */
 def installKitchen(kitchenInit=""){
-    sh """rbenv exec gem install bundler --conservative;
+    sh """rbenv exec gem install bundler -v '~> 1.15.4' --conservative;
           rbenv exec gem install test-kitchen --conservative;"""
     if(kitchenInit!=""){
         sh kitchenInit