Add log for all assigned roles for dynamic cred users

This will help to know what all roles are
assigned to the dynamic cred user.

Change-Id: I052255db0b76cd68e707869ede523d45e3266ee3
diff --git a/tempest/lib/common/dynamic_creds.py b/tempest/lib/common/dynamic_creds.py
index ecbbe8f..5f6d48a 100644
--- a/tempest/lib/common/dynamic_creds.py
+++ b/tempest/lib/common/dynamic_creds.py
@@ -254,6 +254,8 @@
                     user, role, domain)
             elif scope == 'system':
                 self.creds_client.assign_user_role_on_system(user, role)
+        LOG.info("Roles assigned to the user %s are: %s",
+                 user['id'], roles_to_assign)
 
         creds = self.creds_client.get_credentials(**cred_params)
         return cred_provider.TestResources(creds)