Make optional the validation of filters

This fix covers the cases where it's required to be
flexible in the validation of unknown filters.

Change-Id: I1becad77d48556181c5667ad06b2971b8b8517b2
Partially-Implements: blueprint adopt-oslo-versioned-objects-for-db
Closes-Bug: #1622672
diff --git a/neutron/tests/tempest/api/test_subnets.py b/neutron/tests/tempest/api/test_subnets.py
index a3a2e00..4e63a3a 100644
--- a/neutron/tests/tempest/api/test_subnets.py
+++ b/neutron/tests/tempest/api/test_subnets.py
@@ -63,3 +63,7 @@
     @test.idempotent_id('d851937c-9821-4b46-9d18-43e9077ecac0')
     def test_list_no_pagination_limit_0(self):
         self._test_list_no_pagination_limit_0()
+
+    @test.idempotent_id('c0f9280b-9d81-4728-a967-6be22659d4c8')
+    def test_list_validation_filters(self):
+        self._test_list_validation_filters()