qemu-io: fix segment fault when the image format is qed

[root@f15 qemu]# qemu-io -c info /home/zwu/work/misc/rh6.img
format name: qed
cluster size: 64 KiB
vm state offset: 0.000000 bytes
Segmentation fault (core dumped)

This reason is same as the former patch
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

qemu-io.c

@@ -1856,6 +1856,8 @@ int main(int argc, char **argv)
 
     bdrv_init();
 
+    qemu_init_main_loop();
+
     /* initialize commands */
     quit_init();
     help_init();