Fix one case of Item 1 on pantsbuild#11618.

# Rust tests and lints will be skipped. Delete if not intended.
[ci skip-rust]

# Building wheels and fs_util will be skipped. Delete if not intended.
[ci skip-build-wheels]

src/python/pants/pantsd/pants_daemon.py

@@ -201,7 +201,9 @@ def run_sync(self):
             while self._core.is_valid():
                 time.sleep(self.JOIN_TIMEOUT_SECONDS)
 
-            # We're exiting: join the server to avoid interrupting ongoing runs.
+            # We're exiting: purge our metadata to prevent new connections, then join the server
+            # to avoid interrupting ongoing runs.
+            self.purge_metadata(force=True)
             self._logger.info("Waiting for ongoing runs to complete before exiting...")
             native_engine.nailgun_server_await_shutdown(self._server)
             # Then shutdown the PantsDaemonCore, which will shut down any live Scheduler.