Ensure DMRaid /dev entries are created before using named devices

For probed DMRaid devices (when not using libparted DMRaid support)
GParted waits up to 1 second for udev to have processed all events and
created the /dev entries after starting each DMRaid array.  This was
added by this commit from 2009-09-02:
    e7352a5000
    Ensure /dev file system device entries created before adding device

Do the same for devices named on the command line too.

src/GParted_Core.cc

@@ -247,6 +247,7 @@ void GParted_Core::set_devices_thread( std::vector<Device> * pdevices )
 			     dmraid .is_dmraid_device( device_paths[t] ) )
 			{
 				dmraid .create_dev_map_entries( dmraid .get_dmraid_name( device_paths [t] ) ) ;
+				settle_device( 1 );
 			}
 #endif