virsh-volume: Unify alignment of vol-list output columns

virsh-volume: Unify alignment of vol-list output columns

Add an extra space before the first column as we have when listing
domains.

Previous output:

$ virsh vol-list glusterpool
Name                 Path
-----------------------------------------
asdf                 gluster://gluster-node-1/gv0/asdf
c                    gluster://gluster-node-1/gv0/c
cd                   gluster://gluster-node-1/gv0/cd

$ virsh vol-list glusterpool --details
Name  Path                               Type     Capacity  Allocation
----------------------------------------------------------------------
asdf  gluster://gluster-node-1/gv0/asdf  unknown    0.00 B      0.00 B
c     gluster://gluster-node-1/gv0/c     unknown   16.00 B     16.00 B
cd    gluster://gluster-node-1/gv0/cd    unknown    0.00 B      0.00 B

New output:

$ virsh vol-list glusterpool
 Name                 Path
------------------------------------------------------------------------------
 asdf                 gluster://gluster-node-1/gv0/asdf
 c                    gluster://gluster-node-1/gv0/c
 cd                   gluster://gluster-node-1/gv0/cd

$ virsh vol-list glusterpool --details
 Name  Path                               Type     Capacity  Allocation
------------------------------------------------------------------------
 asdf  gluster://gluster-node-1/gv0/asdf  unknown    0.00 B      0.00 B
 c     gluster://gluster-node-1/gv0/c     unknown   16.00 B     16.00 B
 cd    gluster://gluster-node-1/gv0/cd    unknown    0.00 B      0.00 B