remove readlink functions from worker and lz4 fs nodes

[arsnyder16]

Fixes #18587

As mentioned in the bug this manifests in the realpath function. How i stumbled on it was the use of std::filesystem::canonical, std::filesystem::weakly_canonical which uses realpath.

		ssize_t k = readlink(output, stack, p);
		if (k==p) goto toolong;
		if (!k) {
			errno = ENOENT;
			return 0;
		}
		if (k<0) {
                  if (errno != EINVAL) return 0;

if (errno != EINVAL) return 0;