qga/win/installer: add VssOption to installer

Adds registry value VssOption with value 1 to QEMU Guest Agent VSS Provider service registry key

Signed-off-by: Kfir Manor <kfir@daynix.com>
Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>

qga/installer/qemu-ga.wxs

@@ -122,6 +122,10 @@
               <RegistryValue Type="integer" Name="TypesSupported" Value="7" />
               <RegistryValue Type="string" Name="EventMessageFile" Value="[qemu_ga_directory]qemu-ga.exe" />
             </RegistryKey>
+            <RegistryKey Root="HKLM"
+                         Key="System\CurrentControlSet\Services\QEMU Guest Agent VSS Provider">
+              <RegistryValue Type="integer" Name="VssOption" Value="1" />
+            </RegistryKey>
           </Component>
         </Directory>
       </Directory>