Remove CONF values from compute clients

To move compute clients to tempest-lib, this patch moves
CONF values from compute clients to the client setting.

Change-Id: I740d7c20a7b3139b71d120f53bb4764cf51e95e3
diff --git a/tempest/services/compute/json/limits_client.py b/tempest/services/compute/json/limits_client.py
index 66a0649..3a725ae 100644
--- a/tempest/services/compute/json/limits_client.py
+++ b/tempest/services/compute/json/limits_client.py
@@ -16,10 +16,10 @@
 import json
 
 from tempest.api_schema.response.compute.v2 import limits as schema
-from tempest.services.compute.json import base
+from tempest.common import service_client
 
 
-class LimitsClientJSON(base.ComputeClient):
+class LimitsClientJSON(service_client.ServiceClient):
 
     def get_absolute_limits(self):
         resp, body = self.get("limits")