docs/cosa/run: add missing kargs to multipath example
Those kargs are required for sysroot to actually be mounted from the
multipathed target.
@@ -123,10 +123,10 @@ flows. (Many of these flows are covered by our `kola testiso` scenarios.)
### As primary disk
To test multipath on the primary disk in a QEMU instance, use
-`--qemu-multipath`:
+`--qemu-multipath` and add the necessary kargs:
```
-$ cosa run --qemu-multipath
+$ cosa run --qemu-multipath --kargs 'rd.multipath=default root=/dev/disk/by-label/dm-mpath-root rw'
...
[core@cosa-devsh ~]$ findmnt /sysroot
TARGET SOURCE FSTYPE OPTIONS
