Fix bug checksum failures

This commit fixes the bug where multiple realizations try to read checksum at the same time, leading it to grind to a halt.

src/ert/scheduler/job.py

@@ -140,9 +140,9 @@ async def run(
                 break
 
             if self.returncode.result() == 0:
-                if self._scheduler._manifest_queue is not None:
-                    await self._verify_checksum()
                 async with forward_model_ok_lock:
+                    if self._scheduler._manifest_queue is not None:
+                        await self._verify_checksum()
                     await self._handle_finished_forward_model()
                 break