Correct bad use response_strings in live.yaml

response_strings wants a list, not a string. In gabbi earlier than
1.33.0 it accept a string and then iterated checking for each single
character in the response body. So still passing.

This fixes recent failures by putting the necessary '-' at the start
of the search string. It's an easy bug to make and then never
notice, which is why gabbi 1.33.0 is all uptight about it.

Change-Id: I239a968e28a57ad4732f57c10eea7999f5d06349
diff --git a/ceilometer/tests/integration/gabbi/gabbits-live/aodh-gnocchi-threshold-alarm.yaml b/ceilometer/tests/integration/gabbi/gabbits-live/aodh-gnocchi-threshold-alarm.yaml
index daef65c..65b00e9 100644
--- a/ceilometer/tests/integration/gabbi/gabbits-live/aodh-gnocchi-threshold-alarm.yaml
+++ b/ceilometer/tests/integration/gabbi/gabbits-live/aodh-gnocchi-threshold-alarm.yaml
@@ -216,7 +216,7 @@
       data: '"ok"'
       status: 200
       response_strings:
-          "ok"
+          - "ok"
 
     - name: search 'gabbi-gnocchi-threshold-resource-alarm' alarm exist
       desc: search for alarm using user_id, project_id, alarm_name