journal_client: Fix date computations for (un)eventful visits
Fix a wrong computation when several messages (>=3) for the same
snapshot are received in the wrong order
For example, before the fix, the following occurs:
| date | snapshot | | last_ev | last_unev | Snap | | ---- | -------- | --- | -------- | --------- | ---- | | 2022 | S2 | | 2022 | | S2 | | 2020 | S2 | | 2020 | 2022 | S2 | | 2021 | S2 | | **2021** | **2020** | S2 |
as it should be:
| date | snapshot | | last_ev | last_unev | Snap | | ---- | -------- | --- | -------- | --------- | ---- | | 2022 | S2 | | 2022 | | S2 | | 2020 | S2 | | 2020 | 2022 | S2 | | 2021 | S2 | | **2020** | **2022** | S2 |
Related to T3000