ipvs: freeing uninitialized pointer on error

If state != IP_VS_STATE_BACKUP then tinfo->buf is uninitialized.  If
kthread_run() fails then it means we free random memory resulting in an
oops.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>