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>
Merge pull request #1961 from phusl/master-CA-146698

CA-146698: xe vm-retrieve-wlb-recommendations does not print WLB ZeroScoreReason
CA-145689: Adding a message for license server obsolete

Signed-off-by: philippe gabriel <philippe.gabriel@citrix.com>
xe host-apply-edition: avoid race in error reporting

When host.apply_edition raises a license_checkout_error exception, we look at
the recent alerts (messages) to find out the reason for the failure. We seem to
currently miss such an alert every now and then, possibly due to rounding
errors in the used timestamp.  Make this less likely by subtracting a second.

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
xe host-apply-edition: cleanup alert after processing

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
CA-145689: xe host-apply-edition: take into account new v6_license_server_version_obsolete alert

Signed-off-by: Rob Hoes <rob.hoes@citrix.com>
Merge pull request #1962 from robhoes/lic

CA-145689 licensing updates