Use correct types for thresholds

Currently in this template parameters have type Number, but
CloudWatchAlarm has threshold type String. This fix change
Type parameters to String.

Change-Id: If7030063f8bae6b70648a07acb086c341a75373f
diff --git a/tempest/scenario/orchestration/test_autoscaling.yaml b/tempest/scenario/orchestration/test_autoscaling.yaml
index 745eb05..4651284 100644
--- a/tempest/scenario/orchestration/test_autoscaling.yaml
+++ b/tempest/scenario/orchestration/test_autoscaling.yaml
@@ -23,11 +23,11 @@
     Default: '420'
   ScaleUpThreshold:
     Description: Memory percentage threshold to scale up on
-    Type: Number
+    Type: String
     Default: '70'
   ScaleDownThreshold:
     Description: Memory percentage threshold to scale down on
-    Type: Number
+    Type: String
     Default: '60'
   ConsumeMemoryLimit:
     Description: Memory percentage threshold to consume
@@ -182,4 +182,4 @@
             # wait ConsumeStartSeconds then ramp up memory consumption
             # until it is over ConsumeMemoryLimit%
             # then exits ConsumeStopSeconds seconds after stack launch
-            /root/consume_memory > /root/consume_memory.log &
\ No newline at end of file
+            /root/consume_memory > /root/consume_memory.log &