viced: AFSDisk, AFSFetchVolumeStatus Int31 PartSize

viced: AFSDisk, AFSFetchVolumeStatus Int31 PartSize

The AFSDisk and AFSFetchVolumeStatus structures use signed
32-bit integers for representation partition size and
available blocks.  RoundInt64ToInt31() should be used instead
of RoundInt64ToInt32() when assigning their values.

Change-Id: I3834141fce2d54ce8bdfac3dc566074583bb305e
Reviewed-on: http://gerrit.openafs.org/7022
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Tested-by: Derrick Brashear <shadow@dementix.org>
(cherry picked from commit e8f6dfac59fe042a04a9ac5eb3c37356cb3a22a3)
Reviewed-on: http://gerrit.openafs.org/7023
Reviewed-by: Jeffrey Altman <jaltman@secure-endpoints.com>
Tested-by: Jeffrey Altman <jaltman@secure-endpoints.com>