ext4/001: Add ext4 specific test for fallocate zero range

ext4/001: Add ext4 specific test for fallocate zero range

This is based on xfs/242. However it's better to make it file system
specific because the range can be zeroes either directly by writing
zeroes, or converting to unwritten extent, so the actual result might
differ from file system to file system. Also xfs results differ
depending on the page size which is not the case for ext4.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>