Use sxi_cbdata_seterr() calls in functions that have access to curlev_context_t
Fix FreeBSD error and remove unused vars
Check for context reference in case of sxi_cbdata_is_tag fail
Fix check for pointers
Fix error handling in compute_headers_url()

Fix memleak when sxi_sha1_init() fails.
Set error messages while sha update functions fail.
Set rc to -1 to not override stored error messages.
Do not leak cbdata on retry callback
Fix memleak when user callback returns error for file upload
Do not unref cbdata when cluster_query_ev fails

Polling should occur and call cbdata_finish function which eventually should free that pointers.