We can have 2 types of threads open at the same time. One from
the thread view, and another from RHS.
We add another variable to distinguish between the 2 states.
In future, if we have the ability for more than 2 threads, then
we would need to track by threadID.
https://mattermost.atlassian.net/browse/MM-56071
```release-note
NONE
```