vhost-vsock: fix orphan connection reset

local_addr.svm_cid is host cid. We should check guest cid instead,
which is remote_addr.svm_cid. Otherwise we end up resetting all
connections to all guests.

Cc: stable@vger.kernel.org [4.8+]
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Peng Tao <bergwolf@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>