afs: Raise fake free space reporting

We report 'fake' values for free space, free file nodes, etc for the
'AFS' filesystem, since these values are not meaningful for AFS
itself. Currently we report about 9G of free space for most platforms,
and a few different values for a few others. Raise all of these to
2^32-1, so that trying to copy over 9G of data into AFS does not fail
for those applications that check the destination free space with
statfs(2). Note that one such application is KDE 4.8.x.

Consolidate all places that do this, and put the 'fake' value in one
place, AFS_VFS_FAKEFREE, along with the relevant comments.

Related issues reported by Lars Schimmer, Richard Brittain, and
others.

Reviewed-on: http://gerrit.openafs.org/9688
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Markus Koeberl <markus.koeberl@tugraz.at>
Tested-by: Markus Koeberl <markus.koeberl@tugraz.at>
Reviewed-by: D Brashear <shadow@your-file-system.com>
(cherry picked from commit e385571ba37fa6d43fecca17e9e5d60a22a414cd)

Change-Id: Id9b5fa92f48bc83b84bb4f50bc0ae25b028694b0
Reviewed-on: http://gerrit.openafs.org/10984
Tested-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: D Brashear <shadow@your-file-system.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>