Need to fix admin-cli.md user guide for volume part

[shuklanirdesh82]

some of the command sample output is not in sync after #1014

https://github.com/vmware/docker-volume-vsphere/blob/master/docs/user-guide/admin-cli.md#volume

e.g.

[root@localhost:~] /usr/lib/vmware/vmdkops/bin/vmdkops_admin.py ls -h
usage: vmdkops_admin.py ls [-h] [-c Col1,Col2,...]

optional arguments:
  -h, --help        show this help message and exit
  -c Col1,Col2,...  Display selected columns: Choices = ['volume',
                    'datastore', 'created-by', 'created', 'attached-to',
                    'policy', 'capacity', 'used']

[root@localhost:~] /usr/lib/vmware/vmdkops/bin/vmdkops_admin.py ls
Tenant    Volume    Datastore   Created By VM  Created                   Attached To VM (name/uuid)  Policy  Capacity  Used  Disk Format  Filesystem Type  Access Attach As
--------  --------  ----------  -------------  ------------------------  --------------------------  ------  --------  ----  -----------  ---------------  ----------  ----------------------
_DEFAULT  vol1      datastore1  photon-6       Sat Sep 10 01:11:07 2016  detached                    N/A     100MB     13MB  thin         ext4             read-write  independent_persistent

//CC @lipingxue