use prettyPrint for wait

Change-Id: I711913336eaf017ef278709257795a763deacd7a
diff --git a/src/com/mirantis/mk/Aws.groovy b/src/com/mirantis/mk/Aws.groovy
index fe454ab..a016e13 100644
--- a/src/com/mirantis/mk/Aws.groovy
+++ b/src/com/mirantis/mk/Aws.groovy
@@ -176,7 +176,7 @@
             while (true) {
                 // get instances in autoscaling group
                 def out = aws.describeAutoscalingGroup(venv_path, env_vars, group_name)
-                print(out)
+                print(common.prettyPrint(out))
                 def instances = out['AutoScalingGroups'][0]['Instances']
 
                 // check all instances are InService