Don't use Tempest internal methods

All changed methods are clearly internal methods of Tempest, and the
Tempest commit 64e6b4457c748f74bfb4fbf3860ab65b65ae9beb has removed
the internal methods and now the gate issue happens.
This patch makes this project to use better ones instead.

Note: Also had to pull in some fixes from the followup cherry-pick to
make this actually pass well enough to merge.

Related-Bug: #1667824
Change-Id: I901baea1010f05f393919e5ecdd16dc1b322b213
(cherry picked from commit 6ea36282f4)

octavia/tests/tempest/v1/scenario/base.py

@@ -65,9 +65,6 @@ class BaseTestCase(manager.NetworkScenarioTest):
         self.server_ips = {}
         self.server_fixed_ips = {}
 
-        self._create_security_group_for_test()
-        self._set_net_and_subnet()
-
         mgr = self.get_client_manager()
 
         auth_provider = mgr.auth_provider
@@ -84,6 +81,10 @@ class BaseTestCase(manager.NetworkScenarioTest):
             health_monitors_client.HealthMonitorsClient(
                 *self.client_args))
 
+        self.tenant_id = self.load_balancers_client.tenant_id
+        self._create_security_group_for_test()
+        self._set_net_and_subnet()
+
         # admin network client needed for assigning octavia port to flip
         admin_manager = credentials_factory.AdminManager()
         admin_manager.auth_provider.fill_credentials()
@@ -111,12 +112,14 @@ class BaseTestCase(manager.NetworkScenarioTest):
         fallback in absence of tenant networking.
         """
         try:
-            tenant_net = self._list_networks(tenant_id=self.tenant_id)[0]
+            tenant_net = self.admin_manager.networks_client.list_networks(
+                tenant_id=self.tenant_id)['networks'][0]
         except IndexError:
             tenant_net = None
 
         if tenant_net:
-            tenant_subnet = self._list_subnets(tenant_id=self.tenant_id)[0]
+            tenant_subnet = self.admin_manager.subnets_client.list_subnets(
+                tenant_id=self.tenant_id)['subnets'][0]
             self.subnet = tenant_subnet
             self.network = tenant_net
         else:
@@ -126,7 +129,8 @@ class BaseTestCase(manager.NetworkScenarioTest):
             # with the fixed network is the one we want.  In the future, we
             # should instead pull a subnet id from config, which is set by
             # devstack/admin/etc.
-            subnet = self._list_subnets(network_id=self.network['id'])[0]
+            subnet = self.admin_manager.subnets_client.list_subnets(
+                network_id=self.network['id'])['subnets'][0]
             self.subnet = subnet
 
     def _create_security_group_for_test(self):