usb-host: fix host close

The whole usb_host_close() function is skipped in case the device is not
in attached state.  This is wrong though, only then usb_device_detach()
must be skipped, all other cleanup (especially device reset and closing
the file handle) still needs to be done.  There are code paths where
usb_host_close() is called with the device in detached state already.

This fixes usb-host devices not being released and returned to the host
after removing them with device_del.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>