given subdirs, libcurl would still "remember" the full path as if it is the
current directory libcurl is in so that the next curl_easy_perform() would
get really confused if it tried the same path again - as it would not issue
any CWD commands at all, assuming it is already in the "proper" dir.

Starting now, a failed CWD command sets a flag that prevents the path to be
"remembered" after returning.