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/images_client.py b/tempest/services/compute/json/images_client.py
index d64d8d7..c9adc3f 100644
--- a/tempest/services/compute/json/images_client.py
+++ b/tempest/services/compute/json/images_client.py
@@ -18,17 +18,20 @@
 
 from tempest.common.rest_client import RestClient
 from tempest.common import waiters
+from tempest import config
 from tempest import exceptions
 
+CONF = config.CONF
+
 
 class ImagesClientJSON(RestClient):
 
-    def __init__(self, config, username, password, auth_url, tenant_name=None):
-        super(ImagesClientJSON, self).__init__(config, username, password,
+    def __init__(self, username, password, auth_url, tenant_name=None):
+        super(ImagesClientJSON, self).__init__(username, password,
                                                auth_url, tenant_name)
-        self.service = self.config.compute.catalog_type
-        self.build_interval = self.config.compute.build_interval
-        self.build_timeout = self.config.compute.build_timeout
+        self.service = CONF.compute.catalog_type
+        self.build_interval = CONF.compute.build_interval
+        self.build_timeout = CONF.compute.build_timeout
 
     def create_image(self, server_id, name, meta=None):
         """Creates an image of the original server."""