fix: properly handling timeout when revoking ETCD lease

[reinaldooli]

This is a cherrypick from the changes made here.
Since pitaya v3 still using ETCD, these changes needs to be propagated.

[coveralls]

Pull Request Test Coverage Report for Build 19576959475

Details

• 5 of 28 (17.86%) changed or added relevant lines in 3 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.06%) to 58.999%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cluster/etcd_service_discovery.go	0	7	0.0%
pkg/groups/memory_group_service.go	0	7	0.0%
pkg/cluster/nats_rpc_server.go	5	14	35.71%

Files with Coverage Reduction	New Missed Lines	%
pkg/modules/binary.go	2	78.26%

Totals
Change from base Build 19575651066:	-0.06%
Covered Lines:	5068
Relevant Lines:	8590

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💛 - Coveralls