FS-7731: [mod_xml_cdr] url_index global pointer concurrent access fix, curl default connection timeout fix

- thread variable copy of url_index global pointer to prevent the concurrent access having wrong state change if the posting to the current http server was unsuccessfull;
- overriding the default curl connection timeout

Based on need to figure out the smallest block of code need to mutex, and that libcurl (and its wrapper) is definitely thread safe.