Windows: Move VolumeWorkerContext to NonPaged pool

The VolumeWorkerContext contains a KEVENT which must be allocated
from the NonPaged pool.  Move it to the AFSNonPagedVolumeCB struct.

Change-Id: If24ea5f22e6cc7e71328d0d2d8e0c8b9209ce5b2
Reviewed-on: http://gerrit.openafs.org/8992
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>
Windows: Allocated VolumeCB from PagedPool

Only the non-paged portion of the VolumeCB should be allocated
from the non-paged pool.  Allocate the VolumeCB itself from the
paged pool.

Change-Id: If248faf78546bb34fd1ba1ddcc1acb5a6da20c6f
Reviewed-on: http://gerrit.openafs.org/8957
Reviewed-by: Rod Widdowson <rdw@steadingsoftware.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: Jeffrey Altman <jaltman@your-file-system.com>