skip subnetpools tests if default-subnetpools extension not defined

Some subnetpool tests don't have association with certain extension.
This doesn't allow to disable those tests via enabled extensions

Related-prod: PRODX-3721
Change-Id: Ic60654caca3f4fa4473b5cf75872b3131506da11
(cherry picked from commit 91215cac0c54ca7012edaec0c1c6689e041ccd60)
(cherry picked from commit 568ccbb7d548a241db89131c01d799441c3ceb15)
(cherry picked from commit 8d8faf358808449d49e1c5b4e06f75b73f54d1f7)
diff --git a/neutron_tempest_plugin/api/test_subnetpools.py b/neutron_tempest_plugin/api/test_subnetpools.py
index 38c721f..9ab7a49 100644
--- a/neutron_tempest_plugin/api/test_subnetpools.py
+++ b/neutron_tempest_plugin/api/test_subnetpools.py
@@ -28,6 +28,13 @@
 class SubnetPoolsTestBase(base.BaseAdminNetworkTest):
 
     @classmethod
+    def skip_checks(cls):
+        super(SubnetPoolsTestBase, cls).skip_checks()
+        if not utils.is_extension_enabled('default-subnetpools', 'network'):
+            msg = "default-subnetpools extension not enabled."
+            raise cls.skipException(msg)
+
+    @classmethod
     def resource_setup(cls):
         super(SubnetPoolsTestBase, cls).resource_setup()
         min_prefixlen = '29'
@@ -328,7 +335,6 @@
         self.assertIsNone(body['subnetpool']['address_scope_id'])
 
     @decorators.idempotent_id('4c6963c2-f54c-4347-b288-75d18421c4c4')
-    @utils.requires_ext(extension='default-subnetpools', service='network')
     def test_tenant_create_non_default_subnetpool(self):
         """Test creates a subnetpool, the "is_default" attribute is False."""
         created_subnetpool = self._create_subnetpool()