Remove variable assignment that appears twice

Change-Id: I5f775b04f46ce94a580969fdc54b0603ae45a28a
diff --git a/tempest/common/rest_client.py b/tempest/common/rest_client.py
index d649930..fa2ea75 100644
--- a/tempest/common/rest_client.py
+++ b/tempest/common/rest_client.py
@@ -43,7 +43,6 @@
         self.service = None
         self.token = None
         self.base_url = None
-        self.config = config
         self.region = {'compute': self.config.identity.region}
         self.endpoint_url = 'publicURL'
         self.strategy = self.config.identity.strategy