Fix display name for RBAC policies

Now when RBAC policies are selected to delete, the confirmation
message says: "You have selected: . Please confirm your selection."
This patch adds the policy id to the message.

Change-Id: If23ae3760d1199436808a1bf233bc53e9df55ddd

openstack_dashboard/dashboards/admin/rbac_policies/tables.py

@@ -75,6 +75,10 @@ class RBACPoliciesTable(tables.DataTable):
     target_tenant = tables.Column("target_tenant_name",
                                   verbose_name=_("Target Project"))
 
+    def get_object_display(self, datum):
+        """Display name of the RBAC policy."""
+        return datum.id
+
     class Meta(object):
         name = "rbac policies"
         verbose_name = _("RBAC Policies")