Enable PutVCache for FBSD80 and higher

Enable PutVCache for FBSD80 and higher

Matt's patches in a123bd8ccd brought in support for FBSD 7.0, but
also disabled several calls to afs_PutVCache() for FBSD80 and
higher.  Matt says that that patch was focused on 7.0, so the
8.0-related bits may not be relevant.
I have run with the PutVCache calls enabled, and if anything,
my system seems more stable with them.

Change-Id: I8d906848e977d4974e4dcdc151964bb2ac3116b6
Reviewed-on: http://gerrit.openafs.org/1969
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>