Throw an exception when curl_slist_append fails
Throw an exception when curl_slist_append fails

This is likely due to an out of memory error or similar.  Continuing isn't the
correct thing to do: we should throw an exception.

advancedtelematic/aktualizr,advancedtelematic/aktualizr,advancedtelematic/sota_client_cpp,advancedtelematic/aktualizr,advancedtelematic/sota_client_cpp,advancedtelematic/aktualizr