pim6d: "show ipv6 pim state" not displaying when OIL is empty

pim6d: "show ipv6 pim state" not displaying when OIL is empty

Problem:
-------
The cli "show ipv6 pim state" is not displaying when outgoing
interface list is empty.
This is fixed now.

Before Fix:
----------
frr# show ipv6 pim state json
{
  "ffaa::5":{
    "1100::10":{
      "ens224":{
      },
      "installed":1,
      "isRpt":false,
      "refCount":1,
      "oilListSize":0,
      "oilRescan":0,
      "lastUsed":0,
      "packetCount":40,
      "byteCount":3080,
      "wrongInterface":1
    }
  }
}

frr# show ipv6 pim state
Codes: J -> Pim Join, I -> MLD Report, S -> Source, * -> Inherited from (*,G), V -> VxLAN, M -> Muted
 Active  Source  Group  RPT  IIF  OIL

After fix:
---------
Case 1:
- "show ipv6 pim state" output for 1 mroute with 1 oil.

frr# show ipv6 pim state
Codes: J -> Pim Join, I -> MLD Report, S -> Source, * -> Inherited from (*,G), V -> VxLAN, M -> Muted
 Active  Source    Group    RPT  IIF     OIL
 1       1100::10  ffaa::5  n    ens224  ens256( J   )

Case 2:
- "show ipv6 pim state" output for 1 mroute with multiple oil.

frr# show ipv6 pim state
Codes: J -> Pim Join, I -> MLD Report, S -> Source, * -> Inherited from (*,G), V -> VxLAN, M -> Muted
 Active  Source    Group    RPT  IIF     OIL
 1   1100::10   ffaa::5   n   ens224   ens192( J   )
                                       ens256( J   )
Case 3:
- "show ipv6 pim state" output for 1 mroute with no oil

frr# show ipv6 pim state
Codes: J -> Pim Join, I -> MLD Report, S -> Source, * -> Inherited from (*,G), V -> VxLAN, M -> Muted
 Active  Source    Group    RPT  IIF     OIL
 1       1100::10  ffaa::5  n    ens224

Case 4:
- "show ipv6 pim state" output for multiple mroute with multiple oil

frr# show ipv6 pim state
Codes: J -> Pim Join, I -> MLD Report, S -> Source, * -> Inherited from (*,G), V -> VxLAN, M -> Muted
 Active  Source  Group    RPT  IIF     OIL
 1       *       ff05::2  y    ens224  pim6reg(I    )
                                       ens192(I    )
 1       *       ffaa::5  y    ens224  pim6reg(I    )
                                       ens192(I    )

Issue: #13070

Signed-off-by: Sarita Patra <saritap@vmware.com>