Update segment_lun size calculation
Update segment_lun size calculation

Make sure and preseve the actual used size when shrinking vs using a
full stripe

tacketar/lstore,tacketar/lstore,tacketar/lstore,tacketar/lstore,PerilousApricot/lstore,accre/lstore,accre/lstore,PerilousApricot/lstore,accre/lstore,PerilousApricot/lstore,accre/lstore,PerilousApricot/lstore