get_config_opts method was overwritten

outlet_temperature strategy relies on a datasource config parameter,
which can be either "ceilometer" or "gnocchi". This patch overrides
get_config_opts method of base class to allow specify datasource.

Change-Id: I551401039e26816568a04c7f2151d5b3c7ed269a
Closes-Bug: #1709024

watcher/decision_engine/strategy/strategies/outlet_temp_control.py

@@ -30,6 +30,7 @@ telemetries to measure thermal/workload status of server.
 
 import datetime
 
+from oslo_config import cfg
 from oslo_log import log
 
 from watcher._i18n import _
@@ -160,6 +161,16 @@ class OutletTempControl(base.ThermalOptimizationBaseStrategy):
     def granularity(self):
         return self.input_parameters.get('granularity', 300)
 
+    @classmethod
+    def get_config_opts(cls):
+        return [
+            cfg.StrOpt(
+                "datasource",
+                help="Data source to use in order to query the needed metrics",
+                default="ceilometer",
+                choices=["ceilometer", "gnocchi"])
+        ]
+
     def calc_used_resource(self, node):
         """Calculate the used vcpus, memory and disk based on VM flavors"""
         instances = self.compute_model.get_node_instances(node)