Allow to specify the list of sahara enabled plugins

The list of plugins can be tuned by cloud administrator, so make
sure that the list of checked plugins is not hardcoded.
The default list of plugins matches the one currently enabled.

This commit introduces also a new section for data_processing enabled
features in the tempest configuration.

Change-Id: Ie29aeef2df605cfe840e053bc57ff980e9332636
diff --git a/tempest/config.py b/tempest/config.py
index dd693e5..1b6ec62 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -743,6 +743,17 @@
 ]
 
 
+data_processing_feature_group = cfg.OptGroup(
+    name="data_processing-feature-enabled",
+    title="Enabled Data Processing features")
+
+DataProcessingFeaturesGroup = [
+    cfg.ListOpt('plugins',
+                default=["vanilla", "hdp"],
+                help="List of enabled data processing plugins")
+]
+
+
 boto_group = cfg.OptGroup(name='boto',
                           title='EC2/S3 options')
 BotoGroup = [
@@ -1050,6 +1061,7 @@
     (telemetry_group, TelemetryGroup),
     (dashboard_group, DashboardGroup),
     (data_processing_group, DataProcessingGroup),
+    (data_processing_feature_group, DataProcessingFeaturesGroup),
     (boto_group, BotoGroup),
     (stress_group, StressGroup),
     (scenario_group, ScenarioGroup),
@@ -1120,6 +1132,8 @@
         self.telemetry = cfg.CONF.telemetry
         self.dashboard = cfg.CONF.dashboard
         self.data_processing = cfg.CONF.data_processing
+        self.data_processing_feature_enabled = cfg.CONF[
+            'data_processing-feature-enabled']
         self.boto = cfg.CONF.boto
         self.stress = cfg.CONF.stress
         self.scenario = cfg.CONF.scenario