Fix/lock lowdb file (#470)

* Lock data.json while running

* Await floating promises

* Increase retry frequency and attempt count for lock file

* tweak lock retry times

src/commands/send/delete.command.ts

@@ -13,7 +13,7 @@ export class SendDeleteCommand {
     }
 
     try {
-      this.sendService.deleteWithServer(id);
+      await this.sendService.deleteWithServer(id);
       return Response.success();
     } catch (e) {
       return Response.error(e);