MDEV-12893 innodb.log_data_file_size failed in buildbot with InnoDB: Database page corruption

Another fix (work around MDEV-12699): Ensure that the 1234-byte
truncated page is all zero, so that after data file extension
pads the page with zeroes to full page size, the page will read
as a valid one (consisting of zero bytes only).

mysql-test/suite/innodb/t/log_data_file_size.test

@@ -65,6 +65,9 @@ truncate(FILE, $page_size * 4);
 close FILE;
 open(FILE, "+<", "$ENV{'MYSQLD_DATADIR'}test/ibd4f.ibd") or die;
 truncate(FILE, $page_size * 4 + 1234);
+# Work around MDEV-12699 and ensure that the truncated page is all-zero.
+sysseek(FILE, $page_size * 4, 0);
+syswrite(FILE, chr(0) x 1234);
 close FILE;
 open(FILE, "+<", "$ENV{'MYSQLD_DATADIR'}test/ibd5.ibd") or die;
 truncate(FILE, $page_size * 5);