vrf: route: static: T2450: we also need to migrate the interface based routes

Previously during migration if one had used interface routes, the VRF based
ones got not migrated.

The following "old" VyOS 1.3 configuration did not get migrated:

set protocols static interface-route 10.20.0.0/24 next-hop-interface eth2 next-hop-vrf 'blue'
set protocols static interface-route 10.30.0.0/24 next-hop-interface br10 next-hop-vrf 'red'
set protocols vrf blue static interface-route 10.0.0.0/24 next-hop-interface eth1 next-hop-vrf 'default'
set protocols vrf red static interface-route 10.0.0.0/24 next-hop-interface eth1 next-hop-vrf 'default'
set vrf name blue table '3000'
set vrf name mgmt table '1000'
set vrf name red table '2000'

It must get migrated to:

set protocols static route 10.20.0.0/24 interface eth2 vrf 'blue'
set protocols static route 10.30.0.0/24 interface br10 vrf 'red'
set vrf name blue protocols static route 10.0.0.0/24 interface eth1 vrf 'default'
set vrf name blue table '3000'
set vrf name mgmt table '1000'
set vrf name red protocols static route 10.0.0.0/24 interface eth1 vrf 'default'
set vrf name red table '2000'