GFS2: Use reflink for quota data cache

This patch adds reflink support to the quota data cache. It
looks a bit strange because we still don't have a sensible
split in the lookup by id and the lru list. That is coming in
later patches though.

The intent here is just to swap the current ref count for
reflinks in all cases with as little as possible other change.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Abhijith Das <adas@redhat.com>
Tested-by: Abhijith Das <adas@redhat.com>