Description of problem:

In decimal format, Capacity field shows wrong Usable size from volume and total volume size in Volume information in decimal format 

Version-Release number of selected component (if applicable):

[root@darkknightrises ~]# rpm -qa | grep glusterfs
glusterfs-libs-3.7.1-14.el7rhgs.x86_64
glusterfs-fuse-3.7.1-14.el7rhgs.x86_64
glusterfs-3.7.1-14.el7rhgs.x86_64
glusterfs-api-3.7.1-14.el7rhgs.x86_64
glusterfs-cli-3.7.1-14.el7rhgs.x86_64
glusterfs-geo-replication-3.7.1-14.el7rhgs.x86_64
glusterfs-client-xlators-3.7.1-14.el7rhgs.x86_64
glusterfs-server-3.7.1-14.el7rhgs.x86_64

[root@darkknightrises ~]# gstatus --version
gstatus 0.65


How reproducible:
100%

Steps to Reproduce:
1. create 4 node distribute volume 
2. Mount volume as FUSE/NFS on client
3. gstatus -au

Actual results:

85.00 GB(usable from volumes)

Expected results:

83269760/1000
83269.76000000000000000000
83269.7600/1000
83.26976000000000000000

Decimal value can be 84GB  even after round-off but not 85GB

Additional info:

[root@darkknightrises ~]# gstatus -au dec
 
     Product: Community          Capacity:   85.00 GB(raw bricks)
      Status: HEALTHY                       138.00 MB(raw used)
   Glusterfs: 3.7.1                          85.00 GB(usable from volumes)
  OverCommit: No                Snapshots:   0

   Nodes       :  4/  4		  Volumes:   1 Up
   Self Heal   :  0/  0		             0 Up(Degraded)
   Bricks      :  4/  4		             0 Up(Partial)
   Connections :  5/  20                     0 Down

Volume Information
	dist-vol         UP - 4/4 bricks up - Distribute
	                 Capacity: (0% used) 138.00 MB/85.00 GB (used/total)
	                 Snapshots: 0
	                 Self Heal: N/A
	                 Tasks Active: None
	                 Protocols: glusterfs:on  NFS:on  SMB:on
	                 Gluster Connectivty: 5 hosts, 20 tcp connections