Default to using neutron networks_client in get_tenant_network

Proxy apis to neutron like '/os-networks' are deprecated in
microverion 2.36, and calling to them will get 404 error.
So this is to use neutron networks_client as default in get_tenant_network.

https://docs.openstack.org/nova/latest/reference/api-microversion-history.html#id33

Change-Id: I0496d2d0c3c9fe29d61124275c7f5cca78729bf2
diff --git a/tempest/test.py b/tempest/test.py
index 9da85d5..27e0165 100644
--- a/tempest/test.py
+++ b/tempest/test.py
@@ -836,7 +836,7 @@
             manager = cls.get_client_manager()
 
         # Make sure cred_provider exists and get a network client
-        networks_client = manager.compute_networks_client
+        networks_client = manager.networks_client
         cred_provider = cls._get_credentials_provider()
         # In case of nova network, isolated tenants are not able to list the
         # network configured in fixed_network_name, even if they can use it