Migrate resutIndex and requestIndex state inconsistency issue

[penghuo]

Description

• Add sleep 2 seconds between write result index and update state.
  • choose 2 seconds because by default index refresh interval is 1s. add 1s as buffer.
  • sleep 2s does not impact current query latency.
  • sleep 2s increase query latency of query in waiting state. we does not expect much query in the queue, we accept this risk for now.
• It is a migration plan, it does fix the bug.
• Test with script and spark, 50 times, not issue found.

More detail in #171

Issues Resolved

#171

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