wbemprox: Implement Win32_ComputerSystem.NumberOfLogicalProcessors and Win32_ComputerSystem.NumberOfProcessors.

While we're allowed to leave the device in a somewhat inconsistent state after
a failed reset, such a state should be recoverable by calling reset again. If
e.g. mode setting were to fail between the point where we destroy and recreate
the stateblock a subsequent reset would crash because the device doesn't have
a stateblock anymore.