copr-dist-git should mark the workers as done

[praiskup]

--- /usr/bin/copr-distgit-process-import        2022-11-26 23:02:17.000000000 +0000
+++ /usr/bin/copr-distgit-process-import        2022-11-28 19:37:59.733691749 +0000
@@ -55,7 +55,10 @@
         importer.do_import(task)
 
     def handle_task(self):
-        self.handle_import(self.args.build_id)
+        try:
+            self.handle_import(self.args.build_id)
+        finally:
+            self.redis_set_worker_flag("status", "done")