solver: bump id on reset

usadelndsoc/solver.py

@@ -103,6 +103,8 @@ class Solver:
     J_tot = _array_property("_J_tot")
 
     def reset(self):
+        Solver.__global_id += 1
+        self._id = Solver.__global_id
         self._core.reset()
 
     def _solve(