Cannot change "Post as" value for incoming webhook integration II

Description:

Server Setup Information:

• Version of Rocket.Chat Server: 0.60.4
• Operating System: linux 4.9.75-25.55.amzn1.x86_64
• Deployment Method(snap/docker/tar/etc): docker
• Number of Running Instances: 2
• DB Replicaset Oplog: Enabled
• Node Version: v8.9.3

Steps to Reproduce:

1. Create an integration with a valid user in the Post as
2. Edit the Post as and Save

Expected behavior:

The Post as should be changed to the new user

Actual behavior:

1. The Post as change does not persist
2. The value in the Post as does remain as the new value until reload.
3. The icon changes momentarily to the new user then changes back at the bottom of the integration form
4. There is no error message

Relevant logs:

there is nothing in the logs at all relevant to editing the integration.

I tried different users, I tried restarting the server, I tried to change the user while the integration was disabled. All had no effect.

I'll look at the patch for #6869

Start by reproducing the incoming webhook integration edit flow: create an integration, change its Post as user, save it, and reload the form. Trace the save and reload behavior for that field and verify that the selected user remains after reload without errors; the issue names no files or tests to run.