file chooser: Don't open folders unexpectedly
file chooser: Don't open folders unexpectedly

Folders that show up among search results were unexpectedly
returned even for GTK_FILE_CHOOSER_ACTION_OPEN. Change things
around so that we switch to the folder instead, which is the
behavior we had in GTK+ 2.x.

https://bugzilla.gnome.org/show_bug.cgi?id=744204

davidgumberg/gtk,ahodesuka/gtk,davidgumberg/gtk,chergert/gtk,ahodesuka/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,Adamovskiy/gtk,ahodesuka/gtk,alexlarsson/gtk,alexlarsson/gtk,Adamovskiy/gtk,chergert/gtk,ahodesuka/gtk,alexlarsson/gtk,grubersjoe/adwaita,ahodesuka/gtk,ahodesuka/gtk,grubersjoe/adwaita,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,jadahl/gtk,chergert/gtk,jadahl/gtk,jigpu/gtk,Lyude/gtk-,alexlarsson/gtk,jadahl/gtk,jadahl/gtk,jigpu/gtk,grubersjoe/adwaita,ahodesuka/gtk,alexlarsson/gtk,chergert/gtk,Lyude/gtk-,alexlarsson/gtk,chergert/gtk,jigpu/gtk,Lyude/gtk-,chergert/gtk,Adamovskiy/gtk,jadahl/gtk,Adamovskiy/gtk,grubersjoe/adwaita,Adamovskiy/gtk,Lyude/gtk-,davidgumberg/gtk,jigpu/gtk,jigpu/gtk,chergert/gtk,Lyude/gtk-,Adamovskiy/gtk,davidgumberg/gtk,jadahl/gtk,jadahl/gtk,Lyude/gtk-,Lyude/gtk-,Lyude/gtk-,alexlarsson/gtk,davidgumberg/gtk,Adamovskiy/gtk,jigpu/gtk,grubersjoe/adwaita,jigpu/gtk,Adamovskiy/gtk,jadahl/gtk,chergert/gtk,davidgumberg/gtk,ahodesuka/gtk,grubersjoe/adwaita