Delete the default value of domain in role creation

The default value of domain caused the user to be unable to create
role which no domain.
The patch delete the default value of domain.

Change-Id: Ic67b22c435e29f67bafa8e14ab502ebec5b07ec5
Story: 2002671
Task: 22488

heat/engine/resources/openstack/keystone/role.py

@@ -51,9 +51,8 @@ class KeystoneRole(resource.Resource):
         DOMAIN: properties.Schema(
             properties.Schema.STRING,
             _('Name or id of keystone domain.'),
-            default='default',
             constraints=[constraints.CustomConstraint('keystone.domain')],
-            support_status=support.SupportStatus(version='10.0.0')
+            support_status=support.SupportStatus(version='16.0.0')
         )
     }
 

releasenotes/notes/remove-default-domain-from-templates-b5965242bfb78145.yaml

@@ -0,0 +1,13 @@
+---
+prelude: >
+    There was a mismatch between the way heat create role behaved with the
+    templates or with the openstack CLI on what relates to the default domain
+    if the domain is not specified on both cases the CLI will not assign on
+    to the created new role but the heat templates will assign the "default"
+    domain
+critical:
+  - |
+    Templates that creates roles but does not specify the domain will not get
+    a "default" domain from now on. To have a domain added to your new role
+    it needs to be assigned in the template.
+