Don't write thread metadata on flush

The metadata was being written to the final directory, which may be too
slow to accept writes during runtime. The thread metadata needs to be
written anyway at ovni_thread_free() to set the finished flag, so we can
simply skip it.

src/rt/ovni.c

@@ -712,8 +712,6 @@ ovni_flush(void)
 	ovni_ev_set_mcv(&pre, "OF[");
 
 	flush_evbuf();
-	/* Also save metadata */
-	thread_metadata_store();
 
 	ovni_ev_set_clock(&post, ovni_clock_now());
 	ovni_ev_set_mcv(&post, "OF]");