bgpd: Display RPKI validation state if we have it

bgpd: Display RPKI validation state if we have it

When dumping data about prefixes in bgp.  Let's dump the
rpki validation state as well:

Output if rpki is turned on:
janelle# show rpki prefix 2003::/19
Prefix                                   Prefix Length  Origin-AS
2003::                                      19 -  19         3320
janelle# show bgp ipv6 uni 2003::/19
BGP routing table entry for 2003::/19
Paths: (1 available, best #1, table default)
  Not advertised to any peer
  15096 6939 3320
    ::ffff:4113:867a from 65.19.134.122 (193.72.216.231)
    (fe80::e063:daff:fe79:1dab) (used)
      Origin IGP, valid, external, best (First path received), validation-state: valid
      Last update: Sat Mar  6 09:20:51 2021
janelle# show rpki prefix 8.8.8.0/24
Prefix                                   Prefix Length  Origin-AS
janelle# show bgp ipv4 uni 8.8.8.0/24
BGP routing table entry for 8.8.8.0/24
Paths: (1 available, best #1, table default)
  Advertised to non peer-group peers:
  100.99.229.142
  15096 6939 15169
    65.19.134.122 from 65.19.134.122 (193.72.216.231)
      Origin IGP, valid, external, best (First path received), validation-state: not found
      Last update: Sat Mar  6 09:21:25 2021

Example output when rpki is not configured:
eva# show bgp ipv4 uni 8.8.8.0/24
BGP routing table entry for 8.8.8.0/24
Paths: (1 available, best #1, table default)
  Advertised to non peer-group peers:
  janelle(192.168.161.137)
  64539 15096 6939 15169
    192.168.161.137(janelle) from janelle(192.168.161.137) (192.168.44.1)
      Origin IGP, valid, external, bestpath-from-AS 64539, best (First path received)
      Last update: Sat Mar  6 09:33:51 2021

Signed-off-by: Donald Sharp <sharpd@nvidia.com>