xfrm_output_one() does not return a error code when there is
no dst_entry attached to the skb, it is still possible crash
with a NULL pointer dereference in xfrm_output_resume(). Fix
it by return error code -EHOSTUNREACH.
Fixes: 9e1437937807 ("xfrm: Fix NULL pointer dereference when skb_dst_force clears the dst_entry.") Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>