[lib] Remove cookie on logout

Summary:
issue: ENG-6260
If the user tries to log out, but the keyserver doesn't respond, we timeout and dispatch a logout success anyway.
But if the keyserver is down, it won't send a session change. This resulted in us not removing the cookie, and when the server would come back online, the app would reload and the user would be logged in.

We should remove cookie, just like we remove currentUserInfo on logout success.

Test Plan:
Tested that the user is not logged in in the following scenario:

1. login
2. kill the keyserver
3. logout
4. refresh (app not working)
5. run keyserver
6. refresh -> user used to be loogged in, but isn't anymore

Reviewers: kamil, michal

Reviewed By: michal

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D10442