Fix regression in sysUpTime scaling.

When I rewrote the Windows Perfmon datasource to be more efficient by
collecting all counters for an entire device and its components with a
persistent Get-Counter command I forgot to keep sysUpTime scaled to
centi-seconds. This fixes that regression.

The regression happened in 9700394 and de30638.

Fixes ZEN-7264.
Merge pull request #109 from zenoss/feature/ZEN-7264

Please review branch feature/ZEN-7264