fix acquiredb to return promise

Author: pasupulaphani

lib/redis_pool.js

@@ -61,16 +61,15 @@ function RedisPool (name, redisOptions, poolOptions) {
     return _pool.acquire(priority);
   };
 
-  this.acquireDb = (cb, db, priority) => {
-    _pool.acquire((err, client) => {
-      if (!err && client._db_selected !== db) {
-        client["_db_selected"] = db;
-        client.select(db);
-      }
-      debug("DB selected: ", client._db_selected);
-
-      return cb(err, client);
-    }, priority);
+  this.acquireDb = (db, priority) => {
+    return _pool.acquire(priority)
+      .then(client => {
+        if (client._db_selected !== db) {
+          client["_db_selected"] = db;
+          client.select(db);
+        }
+        debug("DB selected: ", client._db_selected);
+      });
   };
 
   // Release a database connection to the pool.