Yes, I'm sure there are tasks those about upgrading vm's hardware version. But i couldnt remove or stop tasks. Task names are like that task-100937**. Hardware version would upgrade the next reboot.
The script:
$do = New-Object -TypeName VMware.Vim.VirtualMachineConfigSpec
$do.ScheduledHardwareUpgradeInfo = New-Object -TypeName VMware.Vim.ScheduledHardwareUpgradeInfo
$do.ScheduledHardwareUpgradeInfo.UpgradePolicy = [VMware.Vim.ScheduledHardwareUpgradeInfoHardwareUpgradePolicy]::onSoftPowerOff
$do.ScheduledHardwareUpgradeInfo.VersionKey = “vmx-19”
$do.Tools = New-Object VMware.Vim.ToolsConfigInfo
$do.Tools.ToolsUpgradePolicy = "UpgradeAtPowerCycle"
foreach($vmName in (Get-Content -Path .\vmlist.txt)){
$vm = Get-VM -Name $vmName
$vm.ExtensionData.ReconfigVM_Task($do)
}