Add name param in setup_test_role

This is to add name param in setup_test_role, only when
name is not specified then random name is generated, thus
setup_test_role can be more widely used to make the code
clean.

Change-Id: Ice8cf92cdbb7294f43cb880997cc5d51f6406f50
diff --git a/tempest/api/identity/base.py b/tempest/api/identity/base.py
index 8317535..5cb4c77 100644
--- a/tempest/api/identity/base.py
+++ b/tempest/api/identity/base.py
@@ -78,9 +78,9 @@
             self.users_client.delete_user, user['id'])
         return user
 
-    def setup_test_role(self, domain_id=None):
+    def setup_test_role(self, name=None, domain_id=None):
         """Set up a test role."""
-        params = {'name': data_utils.rand_name('test_role')}
+        params = {'name': name or data_utils.rand_name('test_role')}
         if domain_id:
             params['domain_id'] = domain_id