if a virtual file change but bothing changed: set it as in sync

if a virtual file change but bothing changed: set it as in sync

some software (at least outlook native software) may fiddle with CfApi
placeholder metadta and set a .msg file to be out of sync state when
opening it

in that case, we will let the sync engine go over it and decide what to
do

it is then possible in that case that we would just put it back in "in
sync" state

Signed-off-by: Matthieu Gallien <matthieu.gallien@nextcloud.com>