This solution does not keep snapshots cache because vz sdk lacks good support
for snapshot related events.

Libvirt and vz sdk has different approach to snapshot ids. vz sdk always
auto generate them while libvirt has ability to specify id by user.
Thus I have no other choice rather than simply ignore ids set by user
or generated by libvirt.
Signed-off-by: NNikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>
Signed-off-by: NMaxim Nestratov <mnestratov@virtuozzo.com>