Move fill_meta_at_scan_start during the scan prepare

bliss/scanning/scan.py

@@ -1278,6 +1278,8 @@ class Scan:
         self._prepare_devices(devices_tree)
         self.writer.prepare(self)
 
+        self._fill_meta("fill_meta_at_scan_start")
+
         self.node.prepared()
 
         self._axes_in_scan = self._get_data_axes(include_calc_reals=True)
@@ -1531,8 +1533,6 @@ class Scan:
                         # starting the scan
                         self._set_state(ScanState.STARTING)
 
-                        self._fill_meta("fill_meta_at_scan_start")
-
                         self._execute_preset("start")
 
                         # this execute iterations