CA-146698: xe vm-retrieve-wlb-recommendations does not print WLB ZeroScoreReason

xe vm-retrieve-wlb-recommendations vm=VMNAME output does not contains ZeroScoreReason field

```
Host(Uuid)                                    : Stars, RecID, ZeroScoreReason
dt57(12f83bfe-7024-4491-8217-98b20afa8433): WLB 4.2414529914529915 472
dt63(c6453ae0-5802-4fee-a75d-b047ebab2c73): WLB 0 471
```

The excepted output result is:

```
Host(Uuid)                                    : Stars, RecID, ZeroScoreReason
dt57(12f83bfe-7024-4491-8217-98b20afa8433): WLB 4.2414529914529915 472 None
dt63(c6453ae0-5802-4fee-a75d-b047ebab2c73): WLB 0 471 Cpu
```

Signed-off-by: Phus Lu <phus.lu@citrix.com>