Multiple global efficacy

This patch update the global efficacy for server consolidation
strategy, test cases and general format.

Change-Id: I62af1e4be415998669f938b3d587c1ccf4293419
Implements: blueprint multiple-global-efficacy-indicator

watcher/decision_engine/solution/efficacy.py

@@ -62,7 +62,7 @@ class Efficacy(object):
         self.indicators = []
         # Used to compute the global efficacy
         self._indicators_mapping = IndicatorsMap()
-        self.global_efficacy = None
+        self.global_efficacy = []
 
     def set_efficacy_indicators(self, **indicators_map):
         """Set the efficacy indicators