Reap dead devices using timeouts. Previously, if a provider died without being able to clean up properly, the device would stay as a ghost.

lib/roles/device.js

@@ -558,6 +558,16 @@ module.exports = function(options) {
     owner = null
   }
 
+  function heartbeat() {
+    push.send([
+      wireutil.heartbeat
+    , wireutil.envelope(new wire.DeviceHeartbeatMessage(
+        options.serial
+      ))
+    ])
+    setTimeout(heartbeat, options.heartbeatInterval)
+  }
+
   function selfDestruct() {
     process.exit(1)
   }
@@ -580,4 +590,6 @@ module.exports = function(options) {
   process.on('SIGTERM', function() {
     gracefullyExit()
   })
+
+  heartbeat()
 }