restore --symlinks --metadata works on symlinks targets

[chrysn]

recovering a filesystem with symlinks pointing outside just erred out trying to chown a non-existent file rather than lchowning it.

it might be sufficient to set O_PATH in the if (restore_metadata) open call.

(sorry i can't test this right now while my big recovery is running, and lost the error msg when i restarted it)

[chrysn]

what made things work was replacing the -1 arguments to the *at functions with AT_FDCWD in the copy_symlink function.