tests: fix broken deduplication check in parallels format test

Original check is broken as supposed reading from 2 different clusters
results in read from the same file offset twice. This is definitely
wrong.

We should be sure that
* the content of both clusters is correct after repair
* clusters are at the different offsets after repair
In order to check the latter we write some content into the first one
and validate that fact.

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
2 files changed