Can't change VCPUs number for VM

[CrazySky]

I tried to change VCPUs number for VM. After changing click ok and vcpu doesn't changed.

1) Ubuntu 16.04
2) 0.r80+dfsg-4
3) VCPU count must be changed
4) Nothing. Changed VCPUs count no effect

Test Case:

Create VM with 1 VCPU count. Stop VM and try to change it via properties.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: openxenmanager 0.r80+dfsg-4
ProcVersionSignature: Ubuntu 4.8.0-52.55~16.04.1-generic 4.8.17
Uname: Linux 4.8.0-52-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.1-0ubuntu2.6
Architecture: amd64
CurrentDesktop: Unity
Date: Tue May 23 13:33:26 2017
InstallationDate: Installed on 2017-05-11 (12 days ago)
InstallationMedia: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
PackageArchitecture: all
SourcePackage: openxenmanager
UpgradeStatus: No upgrade log present (probably fresh install)