Separate backends by type

Adding telemetry_services config group.

Deprecating old gnocchi and sg-core service options.

Splitting the backend specific tests into their own paths so they
can be disabled based on configuration.

Change-Id: I4ca0e217998825589f755d1169aa0600cef14248
diff --git a/telemetry_tempest_plugin/plugin.py b/telemetry_tempest_plugin/plugin.py
index 2f2861e..51c40f9 100644
--- a/telemetry_tempest_plugin/plugin.py
+++ b/telemetry_tempest_plugin/plugin.py
@@ -38,6 +38,9 @@
             conf, tempest_config.telemetry_group,
             tempest_config.TelemetryGroup)
         config.register_opt_group(
+            conf, tempest_config.telemetry_services_group,
+            tempest_config.telemetry_services_opts)
+        config.register_opt_group(
             conf, tempest_config.event_group,
             tempest_config.event_opts)
         config.register_opt_group(
@@ -50,6 +53,8 @@
     def get_opt_lists(self):
         return [(tempest_config.telemetry_group.name,
                  tempest_config.TelemetryGroup),
+                (tempest_config.telemetry_services_group.name,
+                 tempest_config.telemetry_services_opts),
                 (tempest_config.event_group.name,
                  tempest_config.event_opts),
                 (config.service_available_group.name,