[FIX] mail: prevent the server from sending outdated session state

Before this commit, the server could return outdated information to the
client about the state of their own rtc session.

The server should not return information about the client's own rtc
session as the source of truth is the client-side state.

A case in which this was causing an issue was when a user toggled their
mute state right before their client pinged the server and received
outdated session information before their most recent state could be
sent to the server.

This commit fixes this issue.

closes odoo/odoo#78028

X-original-commit: fe991edd
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>