Add log print telling many rows of data were fetched from the database

cdplib/db_handlers/MongodbHandler.py

@@ -275,6 +275,7 @@ class MongodbHandler:
         data = list(data)
         try:
             if len(data)> 0:
+                self._log.info(('{} rows were fetched from the database').format(len(data)))
                 df = pd.DataFrame(data)
                 if index is not None:
                     df.set_index(index, inplace=True)