tests: clean up random sleep time values

[gyuho]

#8762 (comment)

To help maintain the tests and keep flakiness to a minimum, should we establish a set of constants that we references from the integration tests instead? E.g instead of 3 here, maybe have a constant like maxLeaderChangeWait. Once we have a reasonable set of constants, then developers don't need to try to figure out what a good number of seconds is each time they write a test, and if we determine we need to increase the number to minimize test flakes based, we can change it in one place...

#8779 (comment)

as @jpbetz mentioned in other pr, we should define leader election timeout as a const somehere. and normal waiting timeout too. so this could be rewritten to electionWait + retryWait

Also #8757 (comment) and #8795.

/cc @jpbetz @xiang90

[hexfusion]

If this is not been picked up I would like to give it a go.

[xiang90]

@hexfusion sure. thanks.

[stale]

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