bgo#534462: Disable interactive search in the file chooser's shortcuts pane

bgo#534462: Disable interactive search in the file chooser's shortcuts pane

People often do this:
1. Bring up a SAVE dialog
2. Click on a folder in the shortcuts pane
3. Start typing a filename
4. Oops!  The interactive-search entry in the shortcuts pane appears.

With this, the shortcuts pane will not bring up the interactive-search entry.  Then it
will be clear that you are not typing in the right place.

Signed-off-by: Federico Mena Quintero <federico@novell.com>