etcdctl/ctlv3: clarify "lease timetolive" output on expired lease

[gyuho]

Fix #9028.

@hexfusion Could you review? Had to finish this early, to ship this in today's rc release.

[hexfusion]

@gyuho, yes will review this morning.

[hexfusion]

@gyuho, code LGTM, just need to restart semaphoreci and jenkins tests. They did pass locally. Few things:

• Should we bump the license year on these since we are here, even though almost 2018 better then 2016?

• Also should we update timetolive example in https://github.com/coreos/etcd/blob/master/etcdctl/README.md#example-3

./etcdctl lease grant 500
# lease 2d8257079fa1bc0c granted with TTL(500s)

./etcdctl put foo1 bar --lease=2d8257079fa1bc0c
# OK

./etcdctl put foo2 bar --lease=2d8257079fa1bc0c
# OK

./etcdctl lease timetolive 2d8257079fa1bc0c
# lease 2d8257079fa1bc0c granted with TTL(500s), remaining(481s)

./etcdctl lease timetolive 2d8257079fa1bc0c --keys
# lease 2d8257079fa1bc0c granted with TTL(500s), remaining(472s), attached keys([foo2 foo1])

./etcdctl lease timetolive 2d8257079fa1bc0c --write-out=json
# {"cluster_id":17186838941855831277,"member_id":4845372305070271874,"revision":3,"raft_term":2,"id":3279279168933706764,"ttl":465,"granted-ttl":500,"keys":null}

./etcdctl lease timetolive 2d8257079fa1bc0c --write-out=json --keys
# {"cluster_id":17186838941855831277,"member_id":4845372305070271874,"revision":3,"raft_term":2,"id":3279279168933706764,"ttl":459,"granted-ttl":500,"keys":["Zm9vMQ==","Zm9vMg=="]}

./etcdctl lease timetolive 2d8257079fa1bc0c
# lease 2d8257079fa1bc0c already expired 

Thanks!

[codecov-io]

Codecov Report

Merging #9052 into master will decrease coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #9052      +/-   ##
==========================================
- Coverage   76.09%   76.07%   -0.03%     
==========================================
  Files         359      359              
  Lines       29841    29844       +3     
==========================================
- Hits        22707    22703       -4     
- Misses       5556     5567      +11     
+ Partials     1578     1574       -4

Impacted Files	Coverage Δ
etcdctl/ctlv3/command/printer_simple.go	70.62% <100%> (+0.62%)	⬆️
pkg/fileutil/purge.go	73.68% <0%> (-7.9%)	⬇️
etcdctl/ctlv3/command/lease_command.go	65.34% <0%> (-5.95%)	⬇️
mvcc/watchable_store.go	85.97% <0%> (-4.06%)	⬇️
clientv3/leasing/cache.go	87.77% <0%> (-3.34%)	⬇️
etcdserver/api/v3rpc/watch.go	88.58% <0%> (-3.2%)	⬇️
clientv3/concurrency/election.go	79.52% <0%> (-2.37%)	⬇️
raft/node.go	89.38% <0%> (-2.22%)	⬇️
rafthttp/msgappv2_codec.go	69.56% <0%> (-1.74%)	⬇️
clientv3/leasing/kv.go	89.93% <0%> (-1.01%)	⬇️
... and 13 more

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