Repair the locking of the view to the bottom of the scrollbar

... when sorting by date, ascending. It was done in the model with
the assumption that the view would react immediately, but QAIV does it
delayed for quite some time already, so this has to move to the view
instead, inside updateGeometries().

Note that this whole code wasn't supposed to trigger for initial loading,
only when receiving new emails in the current folder, but since akonadi
the loading is async anyway, so there isn't really a notion of initial
loading anymore - and this code triggers during loading too.

Reviewed and tested by Szymon Tomasz Stefanek (pragma).
(cherry picked from commit 818b77885418ddd9e109584a59b9369a3ceea43a)