dolt_status table unhelpful during merge when there are constraint violations.

[timsehn]

Repro:

1. Clone https://www.dolthub.com/repositories/timsehn/three_way_merge
2. In a sql server, merge fire-tim into main

three_way_merge/main> call dolt_merge('fire-tim');
+------+--------------+-----------+-----------------+
| hash | fast_forward | conflicts | message         |
+------+--------------+-----------+-----------------+
|      | 0            | 1         | conflicts found |
+------+--------------+-----------+-----------------+
1 row in set (0.00 sec)

three_way_merge/main> select * from dolt_status;
+------------+--------+----------+
| table_name | staged | status   |
+------------+--------+----------+
| employees  | 0      | modified |
+------------+--------+----------+
1 row in set (0.00 sec)

This should say constraint violation in status instead of modified. In the case of a schema conflict it says:

three_way_merge/main> select * from dolt_status;
+------------+--------+-----------------+
| table_name | staged | status          |
+------------+--------+-----------------+
| employees  | 0      | schema conflict |
+------------+--------+-----------------+