The same logic exists in fd polling. This change is especially important
to avoid busy loop once we limit aio_notify_accept() to blocking
aio_poll().

Cc: qemu-stable@nongnu.org
Signed-off-by: NFam Zheng <famz@redhat.com>
Message-Id: <20180809132259.18402-2-famz@redhat.com>
Signed-off-by: NFam Zheng <famz@redhat.com>
(cherry picked from commit 70232b52)
Signed-off-by: NMichael Roth <mdroth@linux.vnet.ibm.com>