Since cd649efb6b, opening an unread message first does a proc-move,
then proc-view.
Reason is that while we get the (:update ... ) from the move, that only
contains a skeleton message; we need the full view get images etc. This
means that we render the message _twice_.
Here we change add a flag for move to _not_ send the (:update ..), so
only the (:view ...) will trigger rendering of the message.
a4398ac93d