qa/workunits/rados/test_dedup_tool.sh: reset dedup tier during tests

qa/workunits/rados/test_dedup_tool.sh: reset dedup tier during tests

Dedup_tier option needs to be reset whenever every test begins,
because dedup_tier(dedup_chunk_pool) is deleted at the end of each
test---if not, this causes error in case dedup_tier's pool id is
changed.
This commit adds a set command to refresh newly added dedup_tier
pool id.

fixes: https://tracker.ceph.com/issues/58587
cherry picked from commit b2534d90ec22341f42ca262a80613c20d8702b0e

Signed-off-by: Myoungwon Oh <myoungwon.oh@samsung.com>