Fix log file growing to 2x configured cap

log_written tracked bytes since last rotation, not actual file size.
After open_log(), the file could already hold log_max_size bytes but
log_written started at 0, so another log_max_size was written before
rotation triggered. Initialize log_written from the fd position after
rotate_log() so the counter reflects reality.

Author: ricardovfreixo

master.c

@@ -89,6 +89,7 @@ static int open_log(const char *path)
 
 	log_fd = fd;
 	rotate_log();
+	log_written = (size_t)lseek(log_fd, 0, SEEK_CUR);
 	return fd;
 }