libvirt-machine-props: Allow rebooting saved VMs
libvirt-machine-props: Allow rebooting saved VMs

Currently, if user changes the properties of a saved VM that require
reboot to take effect, we don't offer user the option to reboot. As a
result the properties are not in effect when user restores the VM, which
is contrary to what she/he will expect.

This patch:

* offers user the option to reboot saved VMs.
* if user chooses to reboot, the VM is first restored and then rebooted.

https://bugzilla.gnome.org/show_bug.cgi?id=696242

vbenes/gnome-boxes,vbenes/gnome-boxes