remove unused methods from CommonDbMixin

The register_model_query_hook and _apply_dict_extend_functions methods
from CommonDbMixin is not being used by consumers today. This patch
removes them and updates any doc references as well.

NeutronLibImpact

Change-Id: I3e72d7f33f5a7b0c9c023295302929410f94eefb

doc/source/contributor/internals/objects_usage.rst

@@ -109,9 +109,9 @@ and filter it out at DB layer. This can be used by out of tree extensions.
 
 :code:`register_filter_hook_on_model()` is a complementary implementation in
 the :code:`NeutronDbObject` layer to DB layer's
-:code:`register_model_query_hook()`, which adds support for extra filtering
-during construction of SQL query. When extension defines extra query hook, it
-needs to be registered using the objects
+:code:`neutron_lib.db.model_query.register_hook()`, which adds support for
+extra filtering during construction of SQL query. When extension defines
+extra query hook, it needs to be registered using the objects
 :code:`register_filter_hook_on_model()`, if it is not already included in the
 objects :code:`fields`.
 

neutron/db/common_db_mixin.py

@@ -23,13 +23,6 @@ from neutron.db import _resource_extend
 class CommonDbMixin(object):
     """Deprecated."""
 
-    @staticmethod
-    def register_model_query_hook(model, name, query_hook, filter_hook,
-                                  result_filters=None):
-        _model_query.register_hook(
-            model, name, query_hook, filter_hook,
-            result_filters=result_filters)
-
     @staticmethod
     def register_dict_extend_funcs(resource, funcs):
         _resource_extend.register_funcs(resource, funcs)
@@ -50,10 +43,6 @@ class CommonDbMixin(object):
     def _apply_filters_to_query(query, model, filters, context=None):
         return _model_query.apply_filters(query, model, filters, context)
 
-    @staticmethod
-    def _apply_dict_extend_functions(resource_type, response, db_object):
-        _resource_extend.apply_funcs(resource_type, response, db_object)
-
     @staticmethod
     def _get_collection_query(context, model,
                               filters=None, sorts=None,