Setting up driver aliases for keystone domains

Issue: Starting from pike, keystone fails to initialize drivers
       by full path. Error from the log:
       ImportError: (u'Unable to find %(name)r driver in
       %(namespace)r.', {'namespace': 'keystone.identity', 'name':
       'keystone.identity.backends.ldap.Identity'})

Fix:   Use driver aliases taken from keystone egg entry_points.txt

Change-Id: I1dbf916741bd84d4a5e8963d0bfced2b786ac512
diff --git a/tests/pillar/single_domain.sls b/tests/pillar/single_domain.sls
index 68872b3..ec86a26 100644
--- a/tests/pillar/single_domain.sls
+++ b/tests/pillar/single_domain.sls
@@ -39,10 +39,14 @@
           enabled: false
     domain:
       testing:
-        description: "Testing domain"
+        description: "Test domain"
         backend: ldap
+        identity:
+          backend: ldap
+          driver: ldap
         assignment:
           backend: sql
+          driver: keystone.assignment.backends.sql.Assignment
         ldap:
           url: "ldaps://idm.domain.com"
           suffix: "dc=cloud,dc=domain,dc=com"