We still use realpath to validate the path up front, but we pass the
original (DB) path on to the client-side. Passing the resolved path was
wrong anyway for clients that write images across NFS, because the path
the client uses could be different than that computed on the server
(e.g., /proj/foo vs. /.amd_mnt/ops/proj/foo) due to the way mounts are
done. Note that the server will again validate the client-provided path,
so if someone were to mess with a symlink in the path between when
create_image verifies it and when it gets used, there is still no danger.

This will probably eliminate the need for the AMD hack, but I'll leave
it just to be safe.