[server] Budgets created many times for a give period

When getting budgets for a given period, if the budgets don"t exist for this period, the server create them. However, if you try to get budgets, for the same perdiod, twice in a very short time (we talk about ms, but in my case due to a bug in my code, it happened), the budgets to be created might not be already in the database when the second request reaches the server, leading to create twice the budgets.