Create/destroy event listeners

mocha loads all the tests in same process. This means that when
we start a new test, the old state still persists. For event
listeners, this means that they get multiple duplicate event handlers.

src/test/apptask-test.js

@@ -88,6 +88,7 @@ describe('apptask', function () {
         async.series([
             database.initialize,
             appdb.add.bind(null, APP.id, APP.appStoreId, APP.manifest, APP.location, APP.portBindings, APP),
+            settings.initialize,
             settings.setDnsConfig.bind(null, { provider: 'route53', accessKeyId: 'accessKeyId', secretAccessKey: 'secretAccessKey', endpoint: 'http://localhost:5353' }, config.fqdn()),
             settings.setTlsConfig.bind(null, { provider: 'caas' })
         ], done);