libvirt.test: Add more options test for attach-disk

Add some more test for attach-disk, for example:
--serial, --address, --multifunction, --subdriver, etc.

Signed-off-by: Li Yang <liyang.fnst@cn.fujitsu.com>
```
13:56:54 DEBUG| Running '/usr/bin/virsh attach-disk --domain jeos --source /home/yds/autotest/client/tests/virt/shared/attach.img --target vdb --driver qemu --subdriver raw --mode readonly --shareable'
13:56:54 DEBUG| status: 1
13:56:54 DEBUG| stdout: 
13:56:54 DEBUG| stderr: error: option --mode already seen
```

Your using of --mode is strange, right？ You are using --mode readonly and --shareable, so, what exactly mode do you want? readonly? shareable? both? 

From the manpage of virsh:
```
mode can specify the two specific mode readonly or shareable....--shareable is an alias for --mode shareable.
```

You got the command exected with a *Disk attached successfully* is a bug I think. And this problem was fixed by Eric Blake (b9973f526cb12b8e3d751ed19fb071b4a54ea1c0).

It means, your libvirt is too old I guess and your using of here is not correct. Can you post your version of libvirt?