separated DB initialization methods into sql_init

src/services/backup.js

@@ -5,7 +5,7 @@ const optionService = require('./options');
 const fs = require('fs-extra');
 const dataDir = require('./data_dir');
 const log = require('./log');
-const sql = require('./sql');
+const sqlInit = require('./sql_init');
 const syncMutexService = require('./sync_mutex');
 const cls = require('./cls');
 
@@ -60,7 +60,7 @@ if (!fs.existsSync(dataDir.BACKUP_DIR)) {
     fs.mkdirSync(dataDir.BACKUP_DIR, 0o700);
 }
 
-sql.dbReady.then(() => {
+sqlInit.dbReady.then(() => {
     setInterval(cls.wrap(regularBackup), 60 * 60 * 1000);
 
     // kickoff backup immediately