Windows VM crashes when restoring from file if balloon stats polling is enabled

[Impact]

 * Windows VMs BSOD when restoring from QEMUfile or during live migration if the virtio balloon stats polling is enabled.

[Test Case]

 * Install a Windows VM with virtio balloon drivers
 * Start the VM and enable stats polling [1]   
 * Save the VM to savefile [2]
 * Restore the VM [3] 
 * Enable stats polling [1] and VM will BSOD 

QMP examples:
 [1] {"execute":"qom-set","arguments":{"path":"//machine/i440fx/pci.0/child[7]","property":"guest-stats-polling-interval","value":10}} 
 [2] {"execute": "migrate", "arguments": {"uri":"exec:gzip -c > /storage/cases/VM/savefiles/testVM3save.gz"}}
 [3] {"execute":"migrate-incoming","arguments":{"uri":"exec:gzip -c -d /storage/cases/VM/savefiles/testVM3save.gz"}}

[Other Info]

 * This has been fixed upstream with commit 4a1e48becab81020adfb74b22c76a595f2d02a01

[Regression Potential]

 *