wizard: clear skip_review_for_live at end of review
wizard: clear skip_review_for_live at end of review

Since review() is async, it may continue while the LAST page has
already been reached, we want to keep that variable set until review
finishes.

https://bugzilla.gnome.org/show_bug.cgi?id=683417

vbenes/gnome-boxes,vbenes/gnome-boxes