fix ipv6 flag order in worlddump
fix ipv6 flag order in worlddump

this change corrects the flag order from 'route -6'
to '-6 route' as the -6 flag is an option when used with
ip is an argument to the the ip command and not the route
subcommand.

-6 is accpeted as an argument to the standalone 'route'
commannd but not 'ip route' subcommand.

Change-Id: Ic2ae472e42b7b455693d0aade48dc5109e1f21ba

openstack-dev/devstack,nawawi/openstack,openstack-dev/devstack,nawawi/openstack