Wait after switching WAN to failover connection, in order to reduce link flapping.

files/etc/config/wanmonitor

@@ -1,5 +1,6 @@
 config wanmonitor
 	option check_host	'8.8.4.4'
+	option flapping		'60'
 	option interval		'5'
 	option sleep		'0'
 	option wan_primary	'wan1'

files/usr/sbin/wanmonitor

@@ -14,6 +14,7 @@ LOGGER_INFO=6
 LOGGER_DEBUG=7
 
 CHECK_HOST=$(/sbin/uci -q get wanmonitor.@wanmonitor[0].check_host)
+FLAPPING=$(/sbin/uci -q get wanmonitor.@wanmonitor[0].flapping)
 INTERVAL=$(/sbin/uci -q get wanmonitor.@wanmonitor[0].interval)
 SLEEP=$(/sbin/uci -q get wanmonitor.@wanmonitor[0].sleep)
 WAN_PRIMARY=$(/sbin/uci -q get wanmonitor.@wanmonitor[0].wan_primary)
@@ -138,6 +139,7 @@ while true; do
 				/sbin/route add default gw ${GATEWAY_WAN_SECONDARY} metric ${WAN_SECONDARY_METRIC:-0} ${IFNAME_WAN_SECONDARY} &>/dev/null
 			fi
 			WAN=2
+			sleep ${FLAPPING}
 		fi
 	else
 		if [ "${WAN}" = "0" ] || [ "${WAN}" = "2" ]; then