MINOR: log: explicitly handle extra log origins as error when relevant

MINOR: log: explicitly handle extra log origins as error when relevant

Thanks to previous commit, we can know check for log_orig optional flags
in functions taking struct log_orig as parameter. Let's take this
opportunity to add the LOG_ORIG_FL_ERROR flag and check this flag at a
few places to handle the log message differently because if the flag is
set then the caller expects the log to be handled as an error explicitly.

e.g.: in _process_send_log_override(), if the flag is set, use the error
log format instead of the dedicated one.