samples/landlock: Fix path_list memory leak

Clang static analysis reports this error

sandboxer.c:134:8: warning: Potential leak of memory
  pointed to by 'path_list'
        ret = 0;
              ^
path_list is allocated in parse_path() but never freed.
Signed-off-by: Tom Rix <trix@redhat.com>
Link: https://lore.kernel.org/r/20210428213852.2874324-1-trix@redhat.com
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>

samples/landlock/sandboxer.c

@@ -134,6 +134,7 @@ static int populate_ruleset(
 	ret = 0;
 
 out_free_name:
+	free(path_list);
 	free(env_path_name);
 	return ret;
 }