Moved do_execute method to AuditHandler class

Both Continuous and Oneshot audits made same action in
do_execute, so it's a good idea to move it to the base
class

TrivialFix

Change-Id: Ic0353f010509ce45f94126e4db0e629417128ded

watcher/decision_engine/audit/base.py

@@ -74,6 +74,13 @@ class AuditHandler(BaseAuditHandler):
     def strategy_context(self):
         return self._strategy_context
 
+    def do_execute(self, audit, request_context):
+        # execute the strategy
+        solution = self.strategy_context.execute_strategy(
+            audit, request_context)
+
+        return solution
+
     def do_schedule(self, request_context, audit, solution):
         try:
             notifications.audit.send_action_notification(