ospfd: fix no show database output when selecting vrf

ospfd: fix no show database output when selecting vrf

No output when selecting a vrf
frr# show ip ospf vrf default database router adv-router 10.125.0.1
VRF Name: default

       OSPF Router with ID (10.125.0.1)

In comparison with:
frr# show ip ospf database router adv-router 10.125.0.1

       OSPF Router with ID (10.125.0.1)

                Router Link States (Area 0.0.0.0)

  LS age: 155
  Options: 0x2  : *|-|-|-|-|-|E|-
(...)

Signed-off-by: Louis Scalbert <louis.scalbert@6wind.com>