Fix os_user_role issue to grant a role in a domain

Fixes #66525.

Backport of https://github.com/openstack/ansible-collections-openstack/commit/4c03ae.

changelogs/fragments/66525-fix-assing-role-domain-only.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - os_user_role - Fix os_user_role issue to grant a role in a domain.

lib/ansible/modules/cloud/openstack/os_user_role.py

@@ -130,6 +130,7 @@ def main():
     sdk, cloud = openstack_cloud_from_module(module)
     try:
         filters = {}
+        domain_id = None
 
         r = cloud.get_role(role)
         if r is None:
@@ -141,6 +142,7 @@ def main():
             if d is None:
                 module.fail_json(msg="Domain %s is not valid" % domain)
             filters['domain'] = d['id']
+            domain_id = d['id']
         if user:
             if domain:
                 u = cloud.get_user(user, domain_id=filters['domain'])
@@ -155,7 +157,6 @@ def main():
             if g is None:
                 module.fail_json(msg="Group %s is not valid" % group)
             filters['group'] = g['id']
-        domain_id = None
         if project:
             if domain:
                 p = cloud.get_project(project, domain_id=filters['domain'])