Change testing defaults

The world looks broken by our recent changes about that.

So unbreak it. We will fix our N-2 branch testing issue later.

Change-Id: I7ef45463e76a0c17c5016ca46ea4c5162e9fba49
diff --git a/telemetry_tempest_plugin/config.py b/telemetry_tempest_plugin/config.py
index 7ca6e6f..ca16931 100644
--- a/telemetry_tempest_plugin/config.py
+++ b/telemetry_tempest_plugin/config.py
@@ -62,10 +62,10 @@
                help="Granularity to use for aodh alarms. This must match the "
                     "configured Gnocchi archive policy"),
     cfg.StrOpt('alarm_metric_name',
-               default="cpu_util",
+               default="cpu",
                help="Name of the metric to create an alarm on."),
     cfg.StrOpt('alarm_aggregation_method',
-               default="mean",
+               default="rate:mean",
                help="Aggregation method to use for alarm."),
     cfg.IntOpt('alarm_threshold',
                default=10,