storage: prevent quiescence if Raft leadership transfer is in progress

[petermattis]

Add TestReplicaShouldQuiesce to test both the new functionality and the
existing conditions which prevent quiescence.

See #13523

[cockroach-teamcity]

This change is 

[tbg]

, though @bdarnell should take a look as well.

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Reviewed 2 of 2 files at r1, 2 of 2 files at r2.
Review status: all files reviewed at latest revision, 1 unresolved discussion, some commit checks pending.

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pkg/storage/replica.go, line 3749 at r1 (raw file):

	if status.Commit != lastIndex {
		if log.V(4) {
			log.Infof(ctx, "not quiescing: commit (%d) != last-index (%d)",

nit while you're here: s/last-index/lastIndex/

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Comments from Reviewable

[petermattis]

Review status: all files reviewed at latest revision, 1 unresolved discussion, all commit checks successful.

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pkg/storage/replica.go, line 3749 at r1 (raw file):

Previously, tschottdorf (Tobias Schottdorf) wrote…

nit while you're here: s/last-index/lastIndex/

Done.

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Comments from Reviewable

[bdarnell]

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Review status: 1 of 2 files reviewed at latest revision, 2 unresolved discussions, some commit checks pending.

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pkg/storage/replica.go, line 3661 at r2 (raw file):

type quiescer interface {
	Clock() *hlc.Clock

Maybe shouldReplicaQuiesce should take a now hlc.Timestamp instead of having access to a Clock.

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Comments from Reviewable

[petermattis]

Review status: 0 of 2 files reviewed at latest revision, 2 unresolved discussions.

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pkg/storage/replica.go, line 3661 at r2 (raw file):

Previously, bdarnell (Ben Darnell) wrote…

Maybe shouldReplicaQuiesce should take a now hlc.Timestamp instead of having access to a Clock.

I was anxious about there being too many arguments to that method. Let me see what that looks like.

Ok. Done.

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Comments from Reviewable