bgpd: Handle possible non-selection of local route

bgpd: Handle possible non-selection of local route

In rare situations, the local route in a VNI may not get selected as the
best route. One situation is during a race between bgp and zebra which
was addressed in a prior commit. This change addresses another situation
where due to a change of tunnel IP, it is possible that a received route
may be selected as the best route if the path selection needs to take
next hop IPs into consideration. This is a pretty convoluted scenario,
but the code should handle it and delete and withdraw the local route
as well as (re)install the received route.

Ticket: CM-24114
Reviewed By: CCR-9487
Testing Done:
1. Manual tests - note, problem is not readily reproducible
2. evpn-smoke - results documented in the ticket

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