Addresses lp#942382 - refactor configuration for clarity

* Renamed 'nova' to 'compute'
* Merged 'env' with 'compute'
* Created new 'identity' section
* Added defensive code for bad configs

Change-Id: Ifd7506ed82ae2870600a8676a5e811769517a65d
diff --git a/tempest/services/nova/json/servers_client.py b/tempest/services/nova/json/servers_client.py
index e0a26de..35e5782 100644
--- a/tempest/services/nova/json/servers_client.py
+++ b/tempest/services/nova/json/servers_client.py
@@ -6,15 +6,15 @@
 
 class ServersClient(object):
 
-    def __init__(self, config, username, key, auth_url, tenant_name=None):
+    def __init__(self, config, username, password, auth_url, tenant_name=None):
         self.config = config
-        catalog_type = self.config.nova.catalog_type
-        self.client = rest_client.RestClient(config, username, key,
+        catalog_type = self.config.compute.catalog_type
+        self.client = rest_client.RestClient(config, username, password,
                                              auth_url, catalog_type,
                                              tenant_name)
 
-        self.build_interval = self.config.nova.build_interval
-        self.build_timeout = self.config.nova.build_timeout
+        self.build_interval = self.config.compute.build_interval
+        self.build_timeout = self.config.compute.build_timeout
         self.headers = {'Content-Type': 'application/json',
                         'Accept': 'application/json'}