Use pool.pool.release over pool.release (loopbackio#109)

Author: zbarbuto

lib/transaction.js

@@ -69,9 +69,9 @@ function mixinTransaction(PostgreSQL) {
     } else {
       var pool = this.pg;
       if (err) {
-        pool.destroy(connection);
+        pool.pool.destroy(connection);
       } else {
-        pool.release(connection);
+        pool.pool.release(connection);
       }
     }
   };