viced: Move host quota calculation

Calculate this during initialization, not every time we want to use
it.

Reviewed-on: http://gerrit.openafs.org/9710
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 31b518fcf184ba122b6faab54e2e4fa0d37605a3)

Change-Id: Ia4bb30b31e2e3ce25ea16d5932f8f3ae26210c11
Reviewed-on: http://gerrit.openafs.org/10758
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>