Add support to the services decorator for trove

The services decorator previously didn't have support for trove. While
nothing is using it right now it's conceivable in the future. This
commit adds it to the list.

Change-Id: I5c30da6a19243857adf4f19f77181a2545105c21
diff --git a/tempest/test.py b/tempest/test.py
index f04aff7..e9e46ab 100644
--- a/tempest/test.py
+++ b/tempest/test.py
@@ -94,7 +94,8 @@
         'object_storage': CONF.service_available.swift,
         'dashboard': CONF.service_available.horizon,
         'telemetry': CONF.service_available.ceilometer,
-        'data_processing': CONF.service_available.sahara
+        'data_processing': CONF.service_available.sahara,
+        'database': CONF.service_available.trove
     }
     return service_list
 
@@ -108,7 +109,7 @@
     def decorator(f):
         services = ['compute', 'image', 'baremetal', 'volume', 'orchestration',
                     'network', 'identity', 'object_storage', 'dashboard',
-                    'telemetry', 'data_processing']
+                    'telemetry', 'data_processing', 'database']
         for service in args:
             if service not in services:
                 raise exceptions.InvalidServiceTag('%s is not a valid '