test: Fix memleak in test-token cleanup

GCC's asan spotted this:
  Direct leak of 338 byte(s) in 13 object(s) allocated from:
      #0 0x7f54f03fee20 in malloc (/lib64/libasan.so.3+0xc6e20)
      #1 0x445e8c in p11_path_build ../common/path.c:222
      #2 0x4385bd in expand_tempdir ../common/test.c:334
      #3 0x43869c in p11_test_directory ../common/test.c:361
      #4 0x4033e3 in setup_temp ../trust/test-token.c:79

trust/test-token.c

@@ -84,7 +84,6 @@ static void
 teardown (void *path)
 {
 	p11_token_free (test.token);
-	memset (&test, 0, sizeof (test));
 }
 
 static void
@@ -93,6 +92,7 @@ teardown_temp (void *unused)
 	p11_test_directory_delete (test.directory);
 	teardown (test.directory);
 	free (test.directory);
+	memset (&test, 0, sizeof (test));
 }
 
 static void