T4934: ospf: Fix inter-area route summarization

Setting something like protocols ospf area 10 range 10.10.0.0/16 without sub options doesn't work. This is because no range commands are generated when there is no leaf nodes set under the range tag node.

edit protocols ospf
set area 16 network 10.10.0.0/16
set area 16 range 10.10.0.0/16
commit

$ vtysh -c 'show run'
!
router ospf
 auto-cost reference-bandwidth 100
 timers throttle spf 200 1000 10000
 network 10.10.0.0/16 area 16
exit

The generated FRR commands above is missing something like:

area 16 range 10.10.0.0/16