Fix infinite loop when ignore_errors is used with TFRecordDataset

This fix tries to address the issue raised in 25700 where
ignore_errors combined with TFRecordDataset will have a infinite loop.
The issue was that when ignore errors happen, the index of the file names
are not moved forward with error returned. So the same file is repeated.

This fix is a short solution to fix it.

This fix fixes 25700.

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>