centralize all the cron patterns in one place

src/cron.js

@@ -1,11 +1,22 @@
 'use strict';
 
+// IMPORTANT: These patterns are together because they spin tasks which acquire a lock
+// If the patterns overlap all the time, then the task may not ever get a chance to run!
+const DEFAULT_CLEANUP_BACKUPS_PATTERN = '00 30 1,3,5,23 * * *',
+    DEFAULT_BOX_BACKUP_PATTERN_LT_6HOURS = '00 45 1,7,13,19 * * *',
+    DEFAULT_BOX_BACKUP_PATTERN_GT_6HOURS =  '00 45 1,3,5,23 * * *',
+    DEFAULT_BOX_AUTOUPDATE_PATTERN = '00 00 1,3,5,23 * * *',
+    DEFAULT_APP_AUTOUPDATE_PATTERN = '00 15 1,3,5,23 * * *';
+
 exports = module.exports = {
-    startJobs: startJobs,
+    startJobs,
 
-    stopJobs: stopJobs,
+    stopJobs,
 
-    handleSettingsChanged: handleSettingsChanged
+    handleSettingsChanged,
+
+    DEFAULT_BOX_AUTOUPDATE_PATTERN,
+    DEFAULT_APP_AUTOUPDATE_PATTERN
 };
 
 var appHealthMonitor = require('./apphealthmonitor.js'),
@@ -98,7 +109,7 @@ function startJobs(callback) {
     });
 
     gJobs.cleanupBackups = new CronJob({
-        cronTime: '00 45 1,3,5,23 * * *', // every 6 hours. try not to overlap with ensureBackup job
+        cronTime: DEFAULT_CLEANUP_BACKUPS_PATTERN,
         onTick: backups.startCleanupTask.bind(null, auditSource.CRON, NOOP_CALLBACK),
         start: true
     });
@@ -177,9 +188,9 @@ function backupConfigChanged(value, tz) {
     if (gJobs.backup) gJobs.backup.stop();
     let pattern;
     if (value.intervalSecs <= 6 * 60 * 60) {
-        pattern = '00 45 1,7,13,19 * * *'; // no option but to backup in the middle of the day
+        pattern = DEFAULT_BOX_BACKUP_PATTERN_LT_6HOURS; // no option but to backup in the middle of the day
     } else {
-        pattern = '00 45 1,3,5,23 * * *'; // avoid middle of the day backups. it's 45 to not overlap auto-updates
+        pattern = DEFAULT_BOX_BACKUP_PATTERN_GT_6HOURS; // avoid middle of the day backups. it's 45 to not overlap auto-updates
     }
 
     gJobs.backup = new CronJob({