test: fix travis ci

[nolouch]

Signed-off-by: nolouch nolouch@gmail.com

What problem does this PR solve?

go mod tidy failed.

What is changed and how it works?

lazy install goveralls.

Check List

Tests

• Unit test

[codecov-io]

Codecov Report

Merging #2025 into master will increase coverage by <.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2025      +/-   ##
==========================================
+ Coverage   77.46%   77.46%   +<.01%     
==========================================
  Files         180      180              
  Lines       18045    18045              
==========================================
+ Hits        13978    13979       +1     
+ Misses       3014     3012       -2     
- Partials     1053     1054       +1

Impacted Files	Coverage Δ
server/kv/etcd_kv.go	75.32% <0%> (-9.1%)	⬇️
server/heartbeat_streams.go	67% <0%> (-6%)	⬇️
server/member/leader.go	75.51% <0%> (-1.54%)	⬇️
server/tso/tso.go	80.29% <0%> (-0.73%)	⬇️
server/schedule/operator_controller.go	83.57% <0%> (-0.19%)	⬇️
server/grpc_service.go	57.88% <0%> (+0.21%)	⬆️
client/client.go	71.69% <0%> (+0.41%)	⬆️
server/handler.go	51.59% <0%> (+0.45%)	⬆️
server/region_syncer/client.go	82.89% <0%> (+3.94%)	⬆️
pkg/etcdutil/etcdutil.go	88.4% <0%> (+5.79%)	⬆️
... and 1 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update f7f643c...0ac3bc0. Read the comment docs.

[nolouch]

/run-cherry-picker

[sre-bot]

cherry pick to release-3.1 in PR #2029

[nolouch]

/run-cherry-picker

[sre-bot]

cherry pick to release-3.0 failed

[sre-bot]

cherry pick to release-3.0 failed