Tests

Backport ignore old leader's leases revoking request #98

Job	Run time
test (linux-amd64-fmt)	56s
test (linux-amd64-integration-1-cpu)	9m 27s
test (linux-amd64-integration-2-cpu)	9m 46s
test (linux-amd64-integration-4-cpu)	9m 41s
test (linux-amd64-functional)	8m 31s
test (linux-amd64-unit-4-cpu-race)	3m 2s
test (all-build)	3m 38s
test (linux-amd64-grpcproxy)	15m 11s
test (linux-amd64-e2e)	13m 23s
test (linux-386-unit)	2m 10s
	1h 15m 45s

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