[fast/warm reboot] kill radv docker before stopping BGP (sonic-net#608)

* [fast/warm reboot] kill radv docker before stopping BGP

Kill radv docker before stopping BGP. Otherwise it will announce our
departure and cause hosts to lose default gateway.

Signed-off-by: Ying Xie <ying.xie@microsoft.com>

* stop radv service after killing the docker to be ready for service auto restart.

scripts/fast-reboot

@@ -371,6 +371,11 @@ if [[ "$REBOOT_TYPE" = "warm-reboot" || "$REBOOT_TYPE" = "fastfast-reboot" ]]; t
     fi
 fi
 
+# Kill radv before stopping BGP service to prevent annoucing our departure.
+debug "Stopping radv ..."
+docker kill radv &>/dev/null || [ $? == 1 ]
+systemctl stop radv
+
 # Kill bgpd to start the bgp graceful restart procedure
 debug "Stopping bgp ..."
 docker exec -i bgp pkill -9 zebra