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.

tests/ipc_live_test.c

@@ -334,6 +334,9 @@ main(int argc, char **argv)
 		showerrors(&daemon);
 	if(!stopdaemon(&daemon))
 		ok = 0;
+	/* SIGTERM must leave no socket behind. */
+	if(access(live.socket, F_OK) == 0)
+		ok = fail("socket %s survived the daemon", live.socket);
 	if(!closeerrors(&daemon))
 		ok = 0;
 	if(!liveclean(&live))