srv, ibus: remove the endpoints on a signal too

A stopped daemon left its socket and IBus address file behind, since
plan9port ends a process on SIGTERM without running exit handlers. Both
files now go on a note as well as on exit, and only while they are still
the ones this daemon made, so a successor is never robbed of its own.

ibus.c

@@ -69,6 +69,15 @@ unlinkaddr(void)
 	addrino = 0;
 }
 
+static int
+addrnote(void *v, char *note)
+{
+	USED(v);
+	USED(note);
+	unlinkaddr();
+	return 0;
+}
+
 static void
 machineidfiles(char *buf, int sz, char **path, int npath)
 {
@@ -984,6 +993,7 @@ ibusinit(void)
 		goto fail;
 	}
 	cleanupregistered = 1;
+	threadnotify(addrnote, 1);
 	if(writeaddr(addrfile, full) < 0){
 		fprintf(stderr, "strans: ibus: cannot write %s\n", addrfile);
 		goto fail;