fix: use resource disk as placement type (#7931)

Author: awesomenix

e2e/vmss.go

@@ -864,7 +864,8 @@ func getBaseVMSSModel(s *Scenario, customData, cseCmd string) armcompute.Virtual
 						OSType:       to.Ptr(armcompute.OperatingSystemTypesLinux),
 						Caching:      to.Ptr(armcompute.CachingTypesReadOnly),
 						DiffDiskSettings: &armcompute.DiffDiskSettings{
-							Option: to.Ptr(armcompute.DiffDiskOptionsLocal),
+							Option:    to.Ptr(armcompute.DiffDiskOptionsLocal),
+							Placement: to.Ptr(armcompute.DiffDiskPlacementResourceDisk),
 						},
 					},
 				},