toolkit: fix #1510: don't scroll back to focus when view refreshes

toolkit: fix #1510: don't scroll back to focus when view refreshes

adds a workaround, so that we restore the scroll position when we
restore the focus. Fixies an annoying issue where, if a user had an
ellemtn selected, scrolled down and then a store refresh re-rendered
the view it was scrolled back to the selected item and the user lost
his scrolling position.

Add also the 'jumpToFocus' flag to allow enabling the old behaviour

commit e6f2a94f4fff3c125e8406a21d8d6159aca1421e from pve-manager

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>