Create event type alarm for aodh API test

The purpose is to remove dependency of gocchiclient.

Change-Id: I4c07a8d15338b6ec80ca95cef64ab74ed6028319
diff --git a/telemetry_tempest_plugin/aodh/api/base.py b/telemetry_tempest_plugin/aodh/api/base.py
index 1035df7..29b1d61 100644
--- a/telemetry_tempest_plugin/aodh/api/base.py
+++ b/telemetry_tempest_plugin/aodh/api/base.py
@@ -43,10 +43,10 @@
         cls.alarm_ids = []
 
     @classmethod
-    def create_alarm(cls, **kwargs):
+    def create_alarm(cls, type='event', **kwargs):
         body = cls.alarming_client.create_alarm(
             name=data_utils.rand_name('telemetry_alarm'),
-            type='gnocchi_aggregation_by_metrics_threshold', **kwargs)
+            type=type, **kwargs)
         cls.alarm_ids.append(body['alarm_id'])
         return body