This patch requires "Handle BH's queued by AIO completions in
qemu_aio_flush()" to work reliably. The combination of those two
patches survived 300+ migrations with heavy IO load running in the
guest.
Signed-off-by: Nolan Leake <nolan <at> sigbus.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>