ospfd: fix show_ip_ospf_gr_helper

ospfd: fix show_ip_ospf_gr_helper

Fix for the command "show ip ospf vrf NAME graceful-restart helper".
FRR did not show information by vrf's name.
If i have router ospf vrf red, vtysh's command
'show ip ospf vrf red graceful-restart helper' will not show anything.
But command 'show ip ospf vrf all graceful-restart helper' will work
normally. This fix fixes the display of information by vrf's name.

Example:
frr1# show ip ospf vrf vrf-1 graceful-restart helper
VRF Name: vrf-1

       OSPF Router with ID (192.168.255.81)

 Graceful restart helper support enabled.
 Strict LSA check is enabled.
 Helper supported for Planned and Unplanned Restarts.
 Supported Graceful restart interval: 1800(in seconds).

Signed-off-by: teletajp <teletajp@yandex.ru>