Improve savevm consistency by flushing pending AIO before saving.

Index: qemu/vl.c
===================================================================
--- qemu.orig/vl.c	2006-09-03 10:31:48.000000000 +0000
+++ qemu/vl.c	2006-09-03 10:33:51.000000000 +0000
@@ -4551,6 +4551,9 @@
         return;
     }

+    /* Flush pending AIO before saving */
+    qemu_aio_poll();
+
     saved_vm_running = vm_running;
     vm_stop(0);