staging: lustre: Fix an error handling path in 'client_common_fill_super()'

According to error handling path before and after this one, we should go
to 'out_md_fid' here, instead of 'out_md', if 'obd_connect()' fails.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>