util.startup: Fix async waiting for last shutdown steps Observed problem: When shutting down prosody would immediately exit after waiting for s2s connections to close, skipping the last cleanup events and reporting the exit reason and code. This happens because prosody.main_thread is in a waiting state and queuing startup.shutdown is dispatched trough the main loop via nexttick, but since the main loop was no longer running at that point it proceeded to the end of the prosody script and exited there.

--- a/prosody	Sun Jun 12 01:50:33 2022 +0200
+++ b/prosody	Tue Jun 14 16:28:49 2022 +0200
@@ -82,4 +82,4 @@
 
 loop();
 
-thread:run(startup.shutdown);
+startup.exit();