bgpd: backpressure - fix evpn route sync to zebra

In scaled EVPN + ipv4/ipv6 uni route sync to zebra,
some of the ipv4/ipv6 routes skipped reinstallation
due to incorrect local variable's stale value.

Once the local variable value reset in each loop
iteration all skipped routes synced to zebra properly.

Ticket: #3948828

Signed-off-by: Rajasekar Raja <rajasekarr@nvidia.com>
Signed-off-by: Chirag Shah <chirag@nvidia.com>

Author: chiragshah6

bgpd/bgp_zebra.c

@@ -1794,6 +1794,8 @@ static void bgp_handle_route_announcements_to_zebra(struct event *e)
 	bool install;
 
 	while (count < ZEBRA_ANNOUNCEMENTS_LIMIT) {
+		is_evpn = false;
+
 		dest = zebra_announce_pop(&bm->zebra_announce_head);
 
 		if (!dest)