lxd/list: Modify TestColumns to allow for the config:KEY:NAME:WIDTH syntax
lxd/list: Modify TestColumns to allow for the config:KEY:NAME:WIDTH syntax

Signed-off-by: Sava Radoš <93e357e841ff1f06dc3391a307db95db8e34ad90@bitsfactory.com>

mjeanson/lxd,hallyn/lxd,mjeanson/lxd,lxc/lxd,stgraber/lxd,mjeanson/lxd,atxwebs/lxd,hallyn/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,Skarlso/lxd,lxc/lxd,lxc/lxd,stgraber/lxd,hallyn/lxd,lxc/lxd,atxwebs/lxd,hallyn/lxd,stgraber/lxd,hallyn/lxd,Skarlso/lxd,atxwebs/lxd,atxwebs/lxd,hallyn/lxd,lxc/lxd,Skarlso/lxd,stgraber/lxd,lxc/lxd,stgraber/lxd,Skarlso/lxd