Convert all service clients to global CONF object

This commit takes the rest client and all subclass(all the service
clients) and converts all uses of config to the global CONF object.

Partially implements bp config-cleanup

Change-Id: I09525af4f1b308b91d45b7bbea05e0f734ea485c
diff --git a/tempest/services/compute/json/hosts_client.py b/tempest/services/compute/json/hosts_client.py
index 23cb7e9..33e5345 100644
--- a/tempest/services/compute/json/hosts_client.py
+++ b/tempest/services/compute/json/hosts_client.py
@@ -16,14 +16,17 @@
 import urllib
 
 from tempest.common.rest_client import RestClient
+from tempest import config
+
+CONF = config.CONF
 
 
 class HostsClientJSON(RestClient):
 
-    def __init__(self, config, username, password, auth_url, tenant_name=None):
-        super(HostsClientJSON, self).__init__(config, username, password,
+    def __init__(self, username, password, auth_url, tenant_name=None):
+        super(HostsClientJSON, self).__init__(username, password,
                                               auth_url, tenant_name)
-        self.service = self.config.compute.catalog_type
+        self.service = CONF.compute.catalog_type
 
     def list_hosts(self, params=None):
         """Lists all hosts."""