Incorrect assumption that $cache_path is a real path

There is an assumption that $cache_path is a real path.

WP_CONTENT_DIR . "/cache/" can be symlink to the real location.

This causes issues, amongst other places, in wp_cache_confirm_delete() where the real path of $dir is compared to the various cache locations. It will not match when it should.

This assumption also causes admin_bar_delete_page() to fail in the substr() portion of its check and report “Could not delete directory”.