Add support status for current_size ASG attribute

Adds SupportStatus version='2015.1' for `current_size` attribute
of OS::Heat::AutoScalingGroup.

Change-Id: Ib20efc9c8e1cd08fe0b259df381c69ce7f98a41d
Closes-Bug: #1451062

heat/engine/resources/openstack/heat/autoscaling_group.py

@@ -124,7 +124,8 @@ class AutoScalingResourceGroup(aws_asg.AutoScalingGroup):
             support_status=support.SupportStatus(version='2014.2')
         ),
         CURRENT_SIZE: attributes.Schema(
-            _("The current size of AutoscalingResourceGroup.")
+            _("The current size of AutoscalingResourceGroup."),
+            support_status=support.SupportStatus(version='2015.1')
         ),
     }
     update_policy_schema = {}