generic: Add a copy test for overwriting small amounts of data

This test is similar to the previous one, except that it copies one
byte at a time to make sure that this case works as expected.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>
3 files changed