Fix isolated cred cleanup for cli tests

This commit renames the isolated_creds object initialized in the
setupclass for the cli tests. Previously it was using the var cred_prov
which prevented the clear_isolated_creds classmethod from detecting
isolated credentials had been provisioned. This meant that cleanup
was never run which would mean any credentials created or reserved
wouldn't be deleted or unreserved.

Change-Id: I56c270dd719338527d81da9cbd9857f54b76f51a
diff --git a/tempest/cli/__init__.py b/tempest/cli/__init__.py
index 4782129..76aafd8 100644
--- a/tempest/cli/__init__.py
+++ b/tempest/cli/__init__.py
@@ -74,8 +74,8 @@
             msg = "cli testing disabled"
             raise cls.skipException(msg)
         super(ClientTestBase, cls).resource_setup()
-        cls.cred_prov = credentials.get_isolated_credentials(cls.__name__)
-        cls.creds = cls.cred_prov.get_admin_creds()
+        cls.isolated_creds = credentials.get_isolated_credentials(cls.__name__)
+        cls.creds = cls.isolated_creds.get_admin_creds()
 
     def _get_clients(self):
         clients = base.CLIClient(self.creds.username,