daemon: fix memory leak in do_aug_match on realloc failure (#313)

When realloc fails, vp is NULL so free(vp) is a no-op. The original
matches array (and all r strings allocated by aug_match) is leaked.
Use free_stringslen to properly free the array and its contents.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

daemon/augeas.c

@@ -342,7 +342,7 @@ do_aug_match (const char *path)
   vp = realloc (matches, sizeof (char *) * (r+1));
   if (vp == NULL) {
     reply_with_perror ("realloc");
-    free (vp);
+    free_stringslen (matches, r);
     return NULL;
   }
   matches = vp;