Remove the clear of the session server side

This may be related to the issues seen by users to configure the
account. This bug is only confirmed on Firefox on Mac.

The configuration error is a 500 due to a missing 'password' field in
the session, probably related to a clear of the session.

This clear of session only being done on the opening of the /config
page, it could be that Firefox reload the page or re-do a query in the
background, hence clearing the session.

This bug is not reproducible on Chromium nor Firefox on Linux.