Fix ctrl+a behaviour in search field

From: Cosimo Cecchi <cosimoc@gnome.org>
Even when we're not renaming, process events for focused GtkEditables
before activating the menu accels and mnemonics.

https://bugzilla.gnome.org/show_bug.cgi?id=619529
Caja bug: https://github.com/mate-desktop/mate-file-manager/issues/97