wscalls: unflatten payload when calling webservice (#66916)

tests/test_wscall.py

@@ -297,7 +297,7 @@ def test_webservice_with_unflattened_payload_keys(http_requests, pub):
     wscall.request = {
         'method': 'POST',
         'url': 'http://remote.example.net/json',
-        'post_data': {'foo/0': 'first', 'foo/1': 'second', 'name': 'example'},
+        'post_data': {'foo/0': 'first', 'foo/1': 'second', 'bar': 'example'},
     }
     wscall.store()