add watchdog service

modules/watchdog/gaspode.sh

@@ -0,0 +1,23 @@
+#!/bin/sh
+deadline=$(expr $(date +%s) + ${HEADSTART})
+services=$@
+echo started feeding the dog
+exec 3> ${WATCHDOG-/dev/watchdog}
+
+healthy(){
+    test $(date +%s) -le $deadline && return 0
+
+    for i in $services; do
+	if test "$(s6-svstat -o up /run/service/$i)" != "true" ; then
+	   echo "service $i is down"
+	   return 1
+	fi
+    done
+}
+
+while healthy ;do
+    sleep 10
+    echo >&3
+done
+echo "stopped feeding the dog"
+sleep 6000  # don't want s6-rc to restart