MegaRAID: PLUGIN_BUG when no disk found.

```
[fge@megadeth ~]$ sudo lsmenv mega lsmcli ld
Device alias: mega
URI: megaraid://
lsmcli ld
PLUGIN_BUG(2): cmd: '/opt/MegaRAID/storcli/storcli64 /c0/eall/sall show all J', errno: 255, stdout: '{
"Controllers":[
{
        "Command Status" : {
                "Controller" : 0,
                "Status" : "Failure",
                "Description" : "No drive found!"
        }
}
]
}', stderr: ''
```
