bgpd: no router bgp cleanup vrf leaked vpn routes

bgpd: no router bgp cleanup vrf leaked vpn routes

A VRF leak is configured between two vrfs,
bgp VRF X and VRF Y.
When a bgp VRF X is removed, unimport bgp VRF X routes
from VPN and VRF Y.
If VRF X is also importing from bgp VRF Y, remove X from
export list of Y and do required route cleanup.

Ticket:CM-20534 CM-24484
Reviewed By:
Testing Done:

Before deleteing vrf1002:
nl1# show ip route vrf vrf1003 9.9.2.4/32
Routing entry for 9.9.2.4/32
  Known via "bgp", distance 200, metric 0, vrf vrf1003, best
  Last update 00:04:51 ago
  * 200.2.8.2, via swp1.2(vrf vrf1002)
  * 200.2.9.2, via swp2.2(vrf vrf1002)
  * 200.2.10.2, via swp3.2(vrf vrf1002)

Instance vrf1003:
This VRF is importing IPv4 Unicast routes from the following VRFs:
  vrf1002
Import RT(s): 6.0.2.9:2
This VRF is exporting IPv4 Unicast routes to the following VRFs:
  vrf1002
RD: 6.0.3.9:3
Export RT: 6.0.3.9:3

After deleting vrf1002:
nl1(config)# no router bgp 64902 vrf vrf1002

nl1# show ip route vrf vrf1003 9.9.2.4/32
Routing entry for 9.9.2.4/32
  Known via "bgp", distance 20, metric 0, vrf vrf1003, best
  Last update 00:00:32 ago
  * 200.3.8.2, via swp1.3
  * 200.3.9.2, via swp2.3
  * 200.3.10.2, via swp3.3

Instance vrf1003:
This VRF is importing IPv4 Unicast routes from the following VRFs:
  vrf1002
Import RT(s):
This VRF is not exporting IPv4 Unicast routes to any other VRF

nl1# show bgp ipv4 vpn
No BGP prefixes displayed, 0 exist

Readd vrf1002:
points back to source vrf

nl1# show ip route vrf vrf1003 9.9.2.4/32
Routing entry for 9.9.2.4/32
  Known via "bgp", distance 200, metric 0, vrf vrf1003, best
  Last update 00:00:21 ago
  * 200.2.8.2, via swp1.2(vrf vrf1002)
  * 200.2.9.2, via swp2.2(vrf vrf1002)
  * 200.2.10.2, via swp3.2(vrf vrf1002)

Signed-off-by: Chirag Shah <chirag@cumulusnetworks.com>