gfs2: Clean up available revokes accounting

Commit 2129b4288852 ("gfs2: Per-revoke accounting in transactions")
introduced accounting of individual revokes instead of block-wise
accounting, but always assumed that at least one revoke block would be
allocated.  This might lead to confusion and hard-to-track errors later
on, so change the code to let the counting begin at zero revokes.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
5 files changed