On vm stop, vm_running state set to stopped
before device is notified, so callbacks can get envoked with
vm_running = false; and this is not an error.

Cc: qemu-stable@nongnu.org
Acked-by: NJason Wang <jasowang@redhat.com>
Signed-off-by: NMichael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 131c5221)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>