R1:9db4feda09c3

Further corrections to Conpherence updates

Summary:
Apparently I am crazy and didn't test D5537 propertly at all. In particular:

- Currently, the update sends back new "people" and "files" widgets. The "people" widget has a tokenizer, which fatals when the behavior initializes without the widget in the DOM. For now, disable widget updates on replies. I'll fix this in a future diff.
- Currently, we don't update the "last_transaction_id" in the form itself, so the first reply sends back 1 message, the…