net: purge queued packets in tap_cleanup()

If tap has any packets queued at host_net_remove time, it needs to purge
them in order to prevent a sent callback being invoked for it.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

net.c

diff --git a/net.c b/net.c
index cea545e..eb26cd4 100644
--- a/net.c
+++ b/net.c
@@ -1128,6 +1128,8 @@
 {
     TAPState *s = vc->opaque;
 
+    qemu_purge_queued_packets(vc);
+
     if (s->down_script[0])
         launch_script(s->down_script, s->down_script_arg, s->fd);