`show_in_gui` updates do not take effect
Similar to #793 but different...

I have now put a debug line on the `_perform_put` in the service management client.

I can see that the XML is what I'd expect:

``` shell
<OSImage xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/windowsazure"><Label>Red Hat Enterprise Linux 6.8</Label><Eula>http://www.redhat.com/licenses/cloud_CSSA/Red_Hat_Cloud_Software_Subscription_Agreement_for_Microsoft_Azure.pdf</Eula><Description>Red Hat Enterprise Linux is the world\\'s leading enterprise Linux platform built to meet the needs of today\\'s modern enterprise. Red Hat Enterprise Linux is the preferred choice for enterprise Linux workloads on Microsoft Azure. Red Hat Enterprise Linux is an open, reliable, and secure platform designed for customers who want deployment flexibility for their business-critical workloads - from the data center to the Azure cloud - backed by tightly integrated, enterprise-grade support from Red Hat and Microsoft</Description><ImageFamily>Red Hat Enterprise Linux 6.8</ImageFamily><PublishedDate>2016-09-14T07:00:00Z</PublishedDate><ShowInGui>false</ShowInGui><IconUri></IconUri><PrivacyUri>http://www.redhat.com/licenses/cloud_CSSA/Red_Hat_Privacy_Statement_for_Microsoft_Azure.pdf</PrivacyUri><RecommendedVMSize></RecommendedVMSize><SmallIconUri></SmallIconUri><Language></Language></OSImage>
```

But the ShowInGui value for the image isn't actually updated. Is it possible there's an ordering problem here for the values inside `<OSImage>`?

diff --git a/azure-servicemanagement-legacy/azure/servicemanagement/_serialization.py b/azure-servicemanagement-legacy/azure/servicemanagement/_serialization.py
index e732d94dfd..9811e63293 100644
--- a/azure-servicemanagement-legacy/azure/servicemanagement/_serialization.py
+++ b/azure-servicemanagement-legacy/azure/servicemanagement/_serialization.py
@@ -1200,8 +1200,8 @@ class _XmlSerializer(object):
                 ('Eula', image.eula),
                 ('Description', image.description),
                 ('ImageFamily', image.image_family),
-                ('PublishedDate', image.published_date),
                 ('ShowInGui', image.show_in_gui, _lower),
+                ('PublishedDate', image.published_date),
                 ('IconUri', image.icon_uri),
                 ('PrivacyUri', image.privacy_uri),
                 ('RecommendedVMSize', image.recommended_vm_size),
['azure-servicemanagement-legacy/azure/servicemanagement/_serialization.py']