Fix tempest.conf generation

[service_available] isn't being generated. This patch fixes it.

Closes-Bug: #1613542
Change-Id: Ic1ef8f2f9c4e79e0ee35e2e78311d96d00f014e8
diff --git a/ceilometer/tests/tempest/plugin.py b/ceilometer/tests/tempest/plugin.py
index 077a3c2..1a7aa10 100644
--- a/ceilometer/tests/tempest/plugin.py
+++ b/ceilometer/tests/tempest/plugin.py
@@ -40,5 +40,8 @@
                                   tempest_config.TelemetryGroup)
 
     def get_opt_lists(self):
-        return [(tempest_config.telemetry_group.name,
-                 tempest_config.TelemetryGroup)]
+        return [
+            (tempest_config.telemetry_group.name,
+             tempest_config.TelemetryGroup),
+            ('service_available', tempest_config.ServiceAvailableGroup)
+        ]