staging: lustre: lnet/selftest: don't ignore status from lstcon_test_add

If lstcon_test_add sets 'ret' (passed by reference) to 1,
then lst_test_add_ioctl() ignores the return value.
This isn't justified - the return value must be zero for 'ret'
to be meaningful.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>