[REGRESSION] Malformed urls for avatar icons when hosted from a subdirectory

Description:

When rocket chat is hosted from the /chat subdirectory. Avatar icons get requested from broken urls like:

https://my.domain/chat/chat/avatar/%40general?_dc=undefined

I.e. the subdirectory is repeated in the request URL. Seems similar to https://github.com/RocketChat/Rocket.Chat/pull/10029.

This seems to be a regression. I did not have this problem until I upgraded to 0.65.1 from 0.62.2.

Server Setup Information:

• Version of Rocket.Chat Server: 0.65.1
• Operating System: Ubuntu 14.04
• Deployment Method(snap/docker/tar/etc): tar
• Number of Running Instances: 1
• DB Replicaset Oplog: ?
• Node Version: 8.9.1
• mongoDB Version: 3.6.2

Expected behavior:

Client (web and electron) makes successful request to https://my.domain/chat/avatar/%40general?_dc=undefined.

Actual behavior:

Client (web and electron) makes failed request to https://my.domain/chat/chat/avatar/%40general?_dc=undefined.

Start in the web and Electron client code that constructs avatar request URLs, reproducing the /chat subdirectory case described in the issue. Trace why the subdirectory is added twice and verify that both clients request /chat/avatar/%40general rather than /chat/chat/avatar/%40general.