define all server intervals in a map so we can easily clear them all

lib/api.js

@@ -13,6 +13,7 @@ module.exports.create = function (config) {
             config.store = _store;
         }));
     }).nThen(function (w) {
+        // XXX embed this in historyKeeper
         require("../storage/tasks").create(config, w(function (e, tasks) {
             if (e) {
                 throw e;
@@ -20,8 +21,8 @@ module.exports.create = function (config) {
             config.tasks = tasks;
             if (config.disableIntegratedTasks) { return; }
 
-            // XXX support stopping this interval
-            setInterval(function () {
+            config.intervals = config.intervals || {};
+            config.intervals.taskExpiration = setInterval(function () {
                 tasks.runAll(function (err) {
                     if (err) {
                         // either TASK_CONCURRENCY or an error with tasks.list