Rename references to compute networks client

The single network client is going to be split out into multiple
clients, one of which will be called NetworksClient. This patch
renames references to the compute networks client (networks_client)
to avoid confusion or conflicts with the new networks client.

Partially implements blueprint consistent-service-method-names

Change-Id: I1730adb3258557698dbe15658bb1c12f2292c2fd
diff --git a/tempest/common/accounts.py b/tempest/common/accounts.py
index 27b44f6..9e6bee3 100644
--- a/tempest/common/accounts.py
+++ b/tempest/common/accounts.py
@@ -284,7 +284,7 @@
             identity_version=self.identity_version, **creds_dict)
         net_creds = cred_provider.TestResources(credential)
         net_clients = clients.Manager(credentials=credential)
-        compute_network_client = net_clients.networks_client
+        compute_network_client = net_clients.compute_networks_client
         net_name = self.hash_dict['networks'].get(hash, None)
         try:
             network = fixed_network.get_network_from_name(