Use the expanded io log dir when updating the sequence number.

Includes a workaround for older versions of sudo where the
sequence number was stored in the unexpanded io log dir.

plugins/sudoers/sudoers.h

@@ -296,7 +296,7 @@ int atobool(const char *str);
 int get_boottime(struct timeval *);
 
 /* iolog.c */
-void io_nextid(char *iolog_dir, char sessid[7]);
+void io_nextid(char *iolog_dir, char *iolog_dir_fallback, char sessid[7]);
 
 /* iolog_path.c */
 char *expand_iolog_path(const char *prefix, const char *dir, const char *file,