bgpd: modify VRF/view display in show bgp summary

bgpd: modify VRF/view display in show bgp summary

Modify VRF/view display in show bgp summary:
- to be more concise
- to display on which VRF/view no neighbor was found

Before patch:
ubuntu# show bgp vrf all summary

Instance default:

IPv4 Unicast Summary:
BGP router identifier XX.XX.XX.XX, local AS number XXXX vrf-id 0
(...)
IPv6 Unicast Summary:

Instance private:

IPv4 Unicast Summary:

ubuntu# show bgp vrf all ipv4 multicast summary
% No BGP neighbors found
% No BGP neighbors found

After patch:
ubuntu# show bgp vrf all summary

IPv4 Unicast Summary (VRF default):
BGP router identifier XX.XX.XX.XX, local AS number XXXX vrf-id 0
(...)
IPv6 Unicast Summary (VRF default):
(...)
IPv4 Unicast Summary (VRF private):
(...)

ubuntu# show bgp vrf all ipv4 multicast summary
% No BGP neighbors found in VRF default
% No BGP neighbors found in VRF private

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