When using "RESTART" the newly started IRCd could possibly not log or been

missing other functionality.
Reported by DarthGandalf in https://bugs.unrealircd.org/view.php?id=5918

The cause was that all fd's were closed, including 0/1/2. We now reopen
those and map them to /dev/null, like we do later again.

src/misc.c

@@ -2480,6 +2480,7 @@ void server_reboot(const char *mesg)
 		(void)close(2);
 	(void)close(1);
 	(void)close(0);
+	close_std_descriptors();
 	(void)execv(MYNAME, myargv);
 #else
 	close_connections();