worlddump: log command failure details
worlddump: log command failure details

If a command we trigger fails for some reason, it's worth logging
details about the failure (like return code).

Change-Id: Ib19aa474eccdd11e138a4f55e125935b621bca05

openstack-dev/devstack,richliu/devstack,bigswitch/devstack,bigswitch/devstack,group-policy/devstack,samgoon/devstack,dtroyer/devstack,bswartz/devstack,nawawi/openstack,openstack-dev/devstack,noironetworks/devstack,bswartz/devstack,samgoon/devstack,group-policy/devstack,Mahito/devstack,noironetworks/devstack,richliu/devstack,dtroyer/devstack,Mahito/devstack,nawawi/openstack