tests/sstable_perf: fix compaction mode for a multi shard instance
tests/sstable_perf: fix compaction mode for a multi shard instance

Compaction mode fails if more than one shard is used because it doesn't
make sure sstables used as input for compaction only contain local keys.
Therefore, sstable generated by compaction has less keys than expected
because non-local keys are purged out.

Signed-off-by: Raphael S. Carvalho <1e2942cea40e3b4d2162dfcd9e53e41c05a84d22@scylladb.com>
Message-Id: <20181022225153.12029-1-1e2942cea40e3b4d2162dfcd9e53e41c05a84d22@scylladb.com>

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,avikivity/scylla