Fix KeyError in acltemplate plugin (#14115)

Since this method was originally written the python winbind client
bindings have changed so that the key is dns_name instead of alt_name.

src/middlewared/middlewared/plugins/filesystem_/acl_template.py

@@ -206,7 +206,7 @@ async def append_builtins(self, data):
         if 'ACTIVE_DIRECTORY' not in domain_info['domain_flags']['parsed']:
             self.logger.warning(
                 '%s: domain is not identified properly as an Active Directory domain.',
-                domain_info['alt_name']
+                domain_info['dns_name']
             )
             return