Windows: restrict service to 2 cpus by default

Windows: restrict service to 2 cpus by default

Performance drops off considerably when the number of processors
increases due to lock contention and the cm_SyncOp wait processing.
If the MaxCPUs registry value is not set, limit ourselves to two.
Setting MaxCPUs to zero permits use of all CPUs.

Reviewed-on: http://gerrit.openafs.org/6555
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>
(cherry picked from commit 69196e41ec9c5a6ce8efd370fb8582f66667bcf7)

Change-Id: I0cf2d2eeb3d8f7c708e7c365520f10fcd5f22d83
Reviewed-on: http://gerrit.openafs.org/6822
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>