Record number of retries when retrying a task

api.coffee

@@ -236,7 +236,7 @@ else
             response.end('405 Method Not Allowed')
         else if action is '/retry'
           if request.method == 'POST'
-            db.tasksCollection.update({_id : taskId}, {$unset : {fault : 1}}, (err, count) ->
+            db.tasksCollection.update({_id : taskId}, {$unset : {fault : 1}, $inc : {retries : 1}}, (err, count) ->
               response.writeHead(200)
               response.end()
             )