lib: If epoll_ctl() fails, panic instead of just fatal.

This makes it easier to fix such bugs.

src/lib/ioloop-epoll.c

@@ -105,7 +105,7 @@ void io_loop_handle_add(struct io_file *io)
 
 	if (epoll_ctl(ctx->epfd, op, io->fd, &event) < 0) {
 		if (errno == EPERM && op == EPOLL_CTL_ADD) {
-			i_fatal("epoll_ctl(add, %d) failed: %m "
+			i_panic("epoll_ctl(add, %d) failed: %m "
 				"(fd doesn't support epoll%s)", io->fd,
 				io->fd != STDIN_FILENO ? "" :
 				" - instead of '<file', try 'cat file|'");