Show all columns in vmdkops_admin.py ls (remove -l)

[andrewjstone]

Columns shown with ls -l are now the default and the -l option has been removed.
Fixed tests to reflect this and also removed the unused 'last-attached' choice
from the ls -c options.

Tested with make all and CI as well as manually via CLI on ESX.

Fixes #417

[root@localhost:~] /usr/lib/vmware/vmdkops/bin/vmdkops_admin.py ls
Volume     Datastore   Created By    Created                   Attached To  Policy  Capacity  Used
---------  ----------  ------------  ------------------------  -----------  ------  --------  -------
large-vol  datastore1  Ubuntu_15.10  Sat Apr 16 13:34:12 2016  detached     N/A     1.00GB    25.00MB
vol        datastore1  Ubuntu_15.10  Sat Apr 16 20:13:18 2016  detached     N/A     100.00MB  14.00MB
ayo        datastore1  N/A           N/A                       detached     N/A     4.00MB    2.00MB

[msterin]

Nice fix. Please do add 'ls' output result to PR description.
LGMT after that.