Setup resources with network for scenario tests

for all scenario tests, setup network resources with
- network
- subnet with dhcp
- router

Related-Prod: PRODX-26330
Related-Prod: PRODX-26471
Change-Id: Ia10a987eac24c576403f45c2888ae951fac4fcda
diff --git a/barbican_tempest_plugin/tests/scenario/manager.py b/barbican_tempest_plugin/tests/scenario/manager.py
index 8620731..295569b 100644
--- a/barbican_tempest_plugin/tests/scenario/manager.py
+++ b/barbican_tempest_plugin/tests/scenario/manager.py
@@ -31,7 +31,10 @@
 
 # we inherit from NetworkScenarioTest since some test cases need access to
 # check_*_connectivity methods to validate instances are up and accessible
-class ScenarioTest(manager.NetworkScenarioTest):
+# we also inherit from ScenarioTestWithNetwork to get the networking resources
+# pre-setup for us by setup_credentials (network, subnet with dhcp, router)
+class ScenarioTest(manager.ScenarioTestWithNetwork,
+                   manager.NetworkScenarioTest):
     """Base class for scenario tests. Uses tempest own clients. """
     # ## Test functions library
     #
diff --git a/barbican_tempest_plugin/tests/scenario/test_certificate_validation.py b/barbican_tempest_plugin/tests/scenario/test_certificate_validation.py
index 8a0372c..e64952c 100644
--- a/barbican_tempest_plugin/tests/scenario/test_certificate_validation.py
+++ b/barbican_tempest_plugin/tests/scenario/test_certificate_validation.py
@@ -31,11 +31,6 @@
     max_microversion = 'latest'
 
     @classmethod
-    def setup_credentials(cls):
-        cls.set_network_resources(network=True, subnet=True)
-        super().setup_credentials()
-
-    @classmethod
     def resource_setup(cls):
         super(CertificateValidationTest, cls).resource_setup()
         cls.request_microversion = (