tests: json_echo: Drop rule handle before multi-add

Now that JSON parser respects rule handles in explicit add commands, the
still present rule handle causes an error since the old rule does not
exist anymore.

Fixes: 50b5b71ebeee3 ("parser_json: Rewrite echo support")
Signed-off-by: Phil Sutter <phil@nwl.cc>

tests/json_echo/run-test.py

@@ -290,6 +290,7 @@ add_quota["add"]["quota"]["name"] = "q"
 do_flush()
 
 print("doing multi add")
+del(add_rule["add"]["rule"]["handle"])
 add_multi = [ add_table, add_chain, add_set, add_rule ]
 out = do_command(add_multi)