bgp: fix bug of Path(Origin) formatting for show VPNv4 prefix information

The field of 'Path(Origin)' has not displayed in properly ,because Origin codes '2 (incomplete)' is not defined in the latest code .
Therfore, I've patched the codes for formatting as follows .

INFO:bgpspeaker.api.base:API method operator.show called with args: {'params': ['rib', 'all'], 'format': 'cli'}
Status codes: * valid, > best
Origin codes: i - IGP, e - EGP, ? - incomplete
     Network                          Labels   Next Hop             Reason          Metric LocPrf Path
Family: rtfilter
 *>  64512:64511:101                  None     0.0.0.0              Only Path                     ?
Family: vpnv6
Family: vpnv4
 *>  64511:101:10.10.0.1/32           [17]     192.168.100.100      Only Path       0             64511 ?
 *>  64511:101:10.20.2.0/24           [100]    0.0.0.0              Only Path                     ?
 *>  64511:101:10.20.1.0/24           [100]    0.0.0.0              Only Path                     ?
 *>  64511:101:10.20.3.0/24           [100]    0.0.0.0              Only Path                     ?
Family: ipv4
Family: ipv6

Signed-off-by: Toshiki Tsuboi <t.tsubo2000@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>