Fixed segfault due to libcurl connection caching

Fixed segfault due to libcurl connection caching

Libcurl is doing connection caching. When easy handle is cleaned up,
if the handle was previously used by the curl_multi_api, the connection
remains open un the curl multi handle is cleaned up. Some protocols are
sending content like the FTP one, and libcurl try to use the
WRITEFUNCTION or the HEADERFUNCTION. Since structures used in those
callback are freed, we need to use an other callback to which avoid
segfaults.

Libcurl commit d021f2e8a00 fix this issue and should be part of 7.28.2