fix bad parsing of as group

Change-Id: I98bb5fd3f56179b5ca3802f9adb97ce40847688f
diff --git a/src/com/mirantis/mk/Aws.groovy b/src/com/mirantis/mk/Aws.groovy
index e877fff..13d0b04 100644
--- a/src/com/mirantis/mk/Aws.groovy
+++ b/src/com/mirantis/mk/Aws.groovy
@@ -176,8 +176,7 @@
             while (true) {
                 // get instances in autoscaling group
                 def out = aws.describeAutoscalingGroup(venv_path, env_vars, group_name)
-                def out_json = common.parseJSON(out)
-                def instances = out_json['AutoScalingGroups'][0]['Instances']
+                def instances = out['AutoScalingGroups'][0]['Instances']
 
                 // check all instances are InService
                 if (instances.stream().filter{i -> !i['LifecycleState'].equals("InService")}.collect(java.util.stream.Collectors.counting()) == 0) {