gfs2: Revert "ignore negated quota changes"

Commit 4c6a0812 ("gfs2: ignore negated quota changes") skips quota
changes with qd_change == 0 instead of writing them back, which leaves
behind non-zero qd_change values in the affected slots.  The kernel then
assumes that those slots are unused, while the qd_change values on disk
indicate that they are indeed still in use.  The next time the
filesystem is mounted, those invalid slots are read in from disk, which
will cause inconsistencies.

Revert that commit to avoid filesystem corruption.

This reverts commit 4c6a0812.

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