Add skip function for IPv6Test tests

Skip_checks method should be called to check appropriate
parameters (include specific test parameters such as
ipv6_subnet_attributes) before run IPv6Test.

Related-PROD: PRODX-13041

Change-Id: I6e1a0c192a8e8ce62b7437d864f4f4f86563db79
(cherry picked from commit 4d74044f42a026415ed491cf0c72ea81e3278dcb)
diff --git a/neutron_tempest_plugin/scenario/test_ipv6.py b/neutron_tempest_plugin/scenario/test_ipv6.py
index 02e2846..5d65a61 100644
--- a/neutron_tempest_plugin/scenario/test_ipv6.py
+++ b/neutron_tempest_plugin/scenario/test_ipv6.py
@@ -19,6 +19,7 @@
 from tempest.lib.common.utils import data_utils
 from tempest.lib import decorators
 from tempest.lib import exceptions as lib_exc
+import testtools
 
 from neutron_tempest_plugin.common import ip
 from neutron_tempest_plugin.common import ssh
@@ -80,6 +81,12 @@
     ipv6_address_mode = 'slaac'
 
     @classmethod
+    def skip_checks(cls):
+        super(IPv6Test, cls).skip_checks()
+        if not CONF.network_feature_enabled.ipv6:
+            raise cls.skipException("IPv6 is not enabled")
+
+    @classmethod
     @tempest_utils.requires_ext(extension="router", service="network")
     def resource_setup(cls):
         super(IPv6Test, cls).resource_setup()
@@ -163,10 +170,14 @@
             ssh_client=ssh_client, mac_address=ipv6_port['mac_address'])
         self._test_ipv6_address_configured(ssh_client, vm, ipv6_port)
 
+    @testtools.skipUnless(CONF.network_feature_enabled.ipv6_subnet_attributes,
+                          "DHCPv6 attributes are not enabled.")
     @decorators.idempotent_id('b13e5408-5250-4a42-8e46-6996ce613e91')
     def test_ipv6_hotplug_slaac(self):
         self._test_ipv6_hotplug("slaac", "slaac")
 
+    @testtools.skipUnless(CONF.network_feature_enabled.ipv6_subnet_attributes,
+                          "DHCPv6 attributes are not enabled.")
     @decorators.idempotent_id('9aaedbc4-986d-42d5-9177-3e721728e7e0')
     def test_ipv6_hotplug_dhcpv6stateless(self):
         self._test_ipv6_hotplug("dhcpv6-stateless", "dhcpv6-stateless")