Fix a couple of size_t warnings

Fix a couple of size_t warnings

fsprobe/fsprobe.c and kauth/ka-forwarder.c were trying to print size_t's
without using AFS_SIZET_FMT. Fix that.

Reviewed-on: http://gerrit.openafs.org/678
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>