Fix govet

[mkumatag]

Fixes: #9225

[mkumatag]

/cc @gyuho

[codecov-io]

Codecov Report

Merging #9228 into master will increase coverage by 0.01%.
The diff coverage is 53.33%.

@@            Coverage Diff             @@
##           master    #9228      +/-   ##
==========================================
+ Coverage   75.87%   75.88%   +0.01%     
==========================================
  Files         363      363              
  Lines       30161    30161              
==========================================
+ Hits        22884    22889       +5     
+ Misses       5670     5665       -5     
  Partials     1607     1607

Impacted Files	Coverage Δ
clientv3/leasing/txn.go	91.26% <100%> (ø)	⬆️
clientv3/leasing/cache.go	88.88% <100%> (+1.66%)	⬆️
etcdctl/ctlv3/command/move_leader_command.go	68.29% <33.33%> (ø)	⬆️
lease/leasehttp/http.go	63.97% <57.14%> (-1.48%)	⬇️
etcdserver/api/v3rpc/lease.go	78.37% <0%> (-8.11%)	⬇️
clientv3/namespace/watch.go	93.93% <0%> (-6.07%)	⬇️
etcdctl/ctlv3/command/lease_command.go	65.34% <0%> (-5.95%)	⬇️
pkg/testutil/recorder.go	77.77% <0%> (-3.71%)	⬇️
etcdserver/api/v3rpc/watch.go	82.4% <0%> (-3.01%)	⬇️
etcdserver/api/v3election/election.go	64.7% <0%> (-2.95%)	⬇️
... and 15 more

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[mkumatag]

gotip job passed: https://travis-ci.org/coreos/etcd/jobs/333191204

[gyuho]

lgtm. thanks!