Add re-try logic to ssh sync and check

[tellet-q]

Attempt to fix intermittent SSH connection failures (kex_exchange_identification: Connection reset by peer). They are probably caused by server rate limiting or network issues.

• Add retry loop (5 attempts) with ConnectTimeout=30 for rsync operations
• Add retry loop (10 attempts) with ConnectTimeout=10 for SSH readiness checks

[tellet-q]

Example run: https://github.com/qdrant/vector-db-benchmark/actions/runs/20260199241

[KShivendu]

LGTM. Thanks!